Vietnam’s young population and low service costs help give the country a higher internet penetration rate than most of its neighbors in Southeast Asia. Usage of smartphones and related activities, including use of social media and messaging apps, are also fairly high. VIETNAM’S INTERNET PENETRATION IS DRIVEN BY MOBILE PHONES. SMARTPHONE USERS GRAVITATE TO SOCIAL NETWORKS. MESSAGING APPS APPEAL TO THE PRICE CONSCIOUS. LOCAL AND REGIONAL PLAYERS RULE ECOMMERCE. PAYING CUSTOMERS STILL PREFER CABLE AND SATELLITE OVER VIDEOONDEMAND.
Trang 1VIETNAM
ONLINE
Digital Usage and Behavior, 2015-2020
NOVEMBER 2016
Rahul Chadha
Contributor: Dustin Sodano
Trang 2VIETNAM ONLINE: DIGITAL USAGE AND BEHAVIOR, 2015-2020
Vietnam’s young population and low service costs help give the country a higher internet penetration rate than most of its neighbors in Southeast Asia Usage of smartphones and related activities, including use of social media and messaging apps, are also fairly high
■ In 2016, more than half of the country will access the
internet at least once a month—a higher rate than in
India, Indonesia and Thailand
■ According to Nielsen, internet users in Vietnam spend
nearly 25 hours per week online This is high compared
with elsewhere in Southeast Asia
■ One poll found that mobile phones are the most
common device used to access the web in Vietnam,
employed by 85% of internet users ages 15 to 49
Nearly three-quarters (73%) used laptops
■ More than one-third of Vietnam’s population are social
network users By 2020, that figure will approach half
(46.7 million) Smartphones, used by 38.3% of adults
at least monthly, are a main reason behind social
networking’s growth
■ Messaging apps are even more popular One survey
found that 74% of smartphone users used a messaging
service more than once per week, while only 60% had
used social media apps
■ Retail ecommerce sales, excluding travel, will total
$1.71 billion in 2016, accounting for just 1.1% of total
retail sales in Vietnam By 2020, that figure will expand
to only 1.5%
■ Purchasing online video is not yet very common One
poll found that only 13% of internet users in Vietnam
had paid for an online video provider By comparison,
78% had paid for cable TV and 40% had paid for
satellite TV
■ Online video viewers have one destination that stands
out from the rest: YouTube
WHAT’S IN THIS REPORT? This report looks at some of
the most crucial aspects of Vietnam’s digital usage and
behavior, including internet penetration, smartphones and
social networks, messaging apps, ecommerce and video
% of respondents
Average Daily Time Spent Online Among Internet Users in Vietnam, 2015
<3 hours 7%
3-5 hours 26%
5-7 hours 32%
7-9 hours 15%
9+ hours 20%
Note: n=967 ages 15-49 Source: Vietnam Ecommerce and Information Technology Agency (VECITA),
"2015 Vietnam Ecommerce Report," April 15, 2016
210076 www.e Marketer.com
KEY STAT: Internet users in Vietnam tend to spend a great deal of time online In 2015, 58% of users spent an average of 3 to 7 hours daily online, while 20% spent 9 or more hours on the web
CONTENTS
2 Vietnam Online: Digital Usage and Behavior, 2015-2020
3 Vietnam’s Internet Penetration Is Driven by Mobile Phones
4 Smartphone Users Gravitate to Social Networks
6 Messaging Apps Appeal to the Price Conscious
7 Local and Regional Players Rule Ecommerce
10 Paying Customers Still Prefer Cable and Satellite over Video-on-Demand
12 eMarketer Interviews
12 Related eMarketer Content
12 Related Links
12 Editorial and Production Contributors
Trang 3VIETNAM’S INTERNET
PENETRATION IS DRIVEN BY
MOBILE PHONES
Vietnam has one of the higher internet penetration
rates in Southeast Asia thanks to a young population
and low access costs eMarketer estimates that this
year, for the first time, more than half of the country’s
population (50.6%) will access the internet at least
once a month That puts its penetration rate above
India, Indonesia and Thailand The number of internet
users in the country is expected to grow from
48.2 million in 2016 to 61.7 million in 2020, when the
penetration rate will reach 62.5%
Vietnam’s internet growth is complicated by the active
role the government plays in regulation While the
economic reforms begun by the government in 1986—
known collectively as Doi Moi—have liberalized the
country’s economy, the government still monitors online
content and suppresses anything deemed subversive
While the level of control over the internet in Vietnam
does not approach that seen in China, the country’s two
largest internet service providers, Viettel and Vietnam Post
and Telecommunications (VNPT), are state-run entities
However, these controls have not tempered residents’
interest in accessing the internet According to November
2015 data from Nielsen, internet users in Vietnam spent
an average of 24.7 hours per week online, tying them
with internet users in the Philippines, and trailing only
internet users in Singapore, a country with a much more
robust internet infrastructure
hours
Weekly Time Spent Online According to Internet Users in Select Countries in Asia-Pacific, Nov 2015
Note: n=1,000 ages 16+ in each country Source: Nielsen, "Cross-Platform Insights Report 2015" as cited in press release, June 21, 2016
212518 www.e Marketer.com
The amount of time internet users spend online daily was also substantial According to the Vietnam Ecommerce and Information Technology Agency (VECITA), only 7% of internet users in Vietnam spent an average of 3 hours or less online each day in 2015, while 58% spent between 3 and 7 hours
% of respondents
Average Daily Time Spent Online Among Internet Users in Vietnam, 2015
<3 hours 7%
3-5 hours 26%
5-7 hours 32%
7-9 hours 15%
9+ hours 20%
Note: n=967 ages 15-49 Source: Vietnam Ecommerce and Information Technology Agency (VECITA),
"2015 Vietnam Ecommerce Report," April 15, 2016
210076 www.e Marketer.com
For consumers in Vietnam, the route to the internet will increasingly run through mobile devices VECITA also reported that in 2015 mobile phones surpassed laptops as the device most commonly used to access the internet: 85% of internet users ages 15 to 49 said they relied on mobile phones to get online, while 73% of respondents used a laptop
Trang 4% of respondents
Devices Used to Access the Internet Among Internet
Users in Vietnam, 2014 & 2015
Laptop
75%
73%
Mobile phone
65%
85%
Desktop
33%
38%
Tablet
19%
19%
Note: n=967 ages 15-49
Source: Vietnam Ecommerce and Information Technology Agency (VECITA),
"2015 Vietnam Ecommerce Report," April 15, 2016
210077 www.e Marketer.com
Internet access via mobile phones will continue to grow
in part due to the continued adoption of smartphones
in Vietnam eMarketer estimates that the number of
smartphone users in the country will increase from
36.5 million, or 38.3% of the population, this year to
58.4 million users in 2020, when they will account for
59.2% of residents
Mobile Phone* and Smartphone** Users in Vietnam,
2015-2020
Mobile phone users*
(millions)
—% of population
—% change
Smartphone users**
(millions)
—% of population
—% of mobile phone users
—% change
2015 57.1
60.5%
4.4%
27.2
28.8%
47.6%
40.4%
2016 59.2
62.1%
3.7%
36.5
38.3%
61.7%
34.4%
2017 61.0
63.5%
3.1%
43.7
45.5%
71.6%
19.8%
2018 62.9
64.8%
3.1%
49.5
51.0%
78.7%
13.3%
2019 64.5
65.9%
2.6%
54.5
55.6%
84.4%
10.1%
2020 65.9
66.8%
2.2%
58.4
59.2%
88.6%
7.3%
Note: *individuals of any age who own at least one mobile phone and use
the phone(s) at least once per month; **individuals of any age who own at
least one smartphone and use the smartphone(s) at least once per month
Source: eMarketer, Sep 2016
215558 www.e Marketer.com
A May 2016 survey of smartphone users in Asia-Pacific
from research firm GfK found that 81% of respondents in
Vietnam used their devices to access the internet daily
That figure was higher than the one reported for Japan,
India and Australia, underscoring just how fundamental
smartphones have become to gaining internet access
in Vietnam
SMARTPHONE USERS GRAVITATE
TO SOCIAL NETWORKS
Internet users, particularly those on advanced handsets, have been quick to join social networks eMarketer estimates that 35.8 million people in Vietnam will be social network users in 2016, or 37.6%
of the population By 2020, those figures will climb to 46.7 million people and a penetration rate of 47.3%
Social Network Users and Penetration in Vietnam, 2015-2020
2015 2016 2017 2018 2019 2020 Social network users (millions) 32.3 35.8 39.1 42.1 45.1 46.7
—% change 13.8% 10.9% 9.2% 7.8% 6.9% 3.6%
—% of internet users 72.7% 74.2% 75.1% 75.5% 75.6% 75.7%
—% of population 34.2% 37.6% 40.7% 43.4% 46.0% 47.3%
Note: internet users who use a social network via any device at least once per month
Source: eMarketer, Nov 2016
218574 www.e Marketer.com
Kantar Media Vietnam (KMV) found that 80% of internet users ages 15 to 54 in urban areas in Vietnam polled
in 2015 used social networks, making it the most popular internet activity in the survey, tied with visiting news websites
% of respondents
Leading Internet Activities Among Internet Users in Vietnam*, 2015
View video clip 47%
Send/receive emails 39%
Watch TV shows 34%
Academic/research 33%
Note: n=5,775 ages 15-54; *urban areas Source: Kantar Media Vietnam (KMV), "Vietnam Media Habit Survey," May 5, 2016
210817 www.e Marketer.com
Trang 5Smartphones will play a key role in facilitating access to
social networks among internet users Research from
W&S Group found that social media app use was already
deeply entrenched in the behavior of smartphone users
in Vietnam, a mobile-first market According to a poll of
smartphone app users in Vietnam conducted by W&S
Group in March 2016, 84.1% of respondents opened a
social networking app daily
% of respondents
Frequency with Which Smartphone Social Media App
Users in Indonesia, Thailand and Vietnam Use
Smartphone Social Media Apps, March 2016
Indonesia Thailand Vietnam
5-6 times per week 10.7% 7.7% 8.5%
3-4 times per week 3.9% 3.0% 3.0%
1-2 times per week 2.2% 1.5% 3.6%
Less than once per week 2.4% 0.9% 0.8%
Note: Indonesia n=460; Thailand n=465; Vietnam n=504; ages 17+;
respondents referred to their most used social media apps in the past 30
days; numbers may not add up to 100% due to rounding
Source: W&S Group, "Tracking Study on Smartphone Applications," May 11,
2016
210840 www.e Marketer.com
In addition, W&S Group reported that 84.0% of
smartphone users in Vietnam had opened a social
networking app sometime in the 30 days preceding its
March 2016 poll That put social networking apps ahead of
other app categories in the poll, including games, music,
and photo and video apps
Facebook has already established a strong presence in
Vietnam, with an estimated 91.5% of all social network
users in the country accessing the platform in 2016
eMarketer projects the number of Facebook users in
Vietnam will increase from 32.7 million this year (34.4%
of the population) to 43.5 million (44.1%) in 2020
Facebook Users and Penetration in Vietnam,
2015-2020
2015 2016 2017 2018 2019 2020 Facebook users (millions) 29.4 32.7 36.0 39.0 41.9 43.5
—% change 14.5% 11.5% 9.8% 8.4% 7.5% 3.8%
—% of social network users 91.0% 91.5% 92.0% 92.5% 93.0% 93.2%
—% of internet users 66.2% 67.9% 69.1% 69.8% 70.3% 70.5%
—% of population 31.1% 34.4% 37.4% 40.2% 42.8% 44.1%
Note: internet users who access their Facebook account via any device at
least once per month
Source: eMarketer, Nov 2016
218786 www.e Marketer.com
Facebook’s dominance over competing social networks in Vietnam also extends to smartphones According to We Are Social, Facebook’s social media app had a penetration rate of 29% among the overall population as of Q4 2015, putting it ahead of local chat app Zalo, Google+, Line, Twitter and Instagram, among other social media and messaging platforms
% of population
Social Media/Messaging App User Penetration in Vietnam, by Platform, Q4 2015
Instagram 9%
WhatsApp 6%
Source: We Are Social, "Digital in 2016," Jan 27, 2016
204245 www.e Marketer.com
While Facebook has experienced success in capturing market share, its gains also face a potential threat Vietnam’s government has shown a willingness to block the platform at moments of political unrest, as when protesters gathered for rallies in May 2016 following mass fish deaths attributed to pollution released into waters from a plastics manufacturing company
While Facebook once faced competition from local upstart Zing Me, the latter was unable to keep pace with the innovations offered by Mark Zuckerberg’s company, and was eventually abandoned by users Now Facebook
is the clear leader in Vietnam, with a penetration rate that will be hard for competitors to reach or even approach
Trang 6MESSAGING APPS APPEAL TO
THE PRICE CONSCIOUS
In Vietnam, messaging apps are broadly adopted by
smartphone users for a simple reason—they provide
users with over-the-top (OTT) services that allow
customers to avoid sometimes costly texting services
provided by mobile network operators
The GfK survey found that 74% of smartphone users in
Vietnam used a messaging service more than once per
week, a higher figure than those who used either social
media (60%) or shopping apps (31%)
% of respondents
Smartphone Users in Asia-Pacific Who Use
Smartphone Messaging, Social Media and Shopping
Apps Regularly*, by Country, May 2016
Messaging Social media Shopping
Note: n=8,099 ages 18+; *more than once per week
Source: GfK, "The Connected Consumer: Insights into Digital Consumer
Behavior in APAC," June 22, 2016
213791 www.e Marketer.com
Messaging app users in Vietnam have embraced local
platform Zalo in a market that is now crowded with
international competitors According to DI Marketing,
80% of smartphone users polled in June 2016 had Zalo
installed on their devices, more than the 73% who
had installed Facebook Messenger Global messaging
giants WeChat and WhatsApp barely registered among
smartphone users in Vietnam, with install rates of 5% and
4%, respectively
% of respondents in each group
Messaging Apps that Smartphone Users in Vietnam Have Installed on Their Smartphone, by Age, June 2016
18-25 26-30 30-35 35+ Total
Facebook Messenger 78% 72% 75% 55% 73%
Note: n=1,200 Source: DI Marketing, "Chat Apps Usage in Vietnam," June 10, 2016
212098 www.e Marketer.com
Zalo’s parent company, VNG, reported in April 2016 that its messaging app had 50 million registered users Despite its near ubiquity among smartphone users in Vietnam, Zalo still faces a formidable opponent in Facebook Messenger, which had nearly the same install rate as Zalo among those ages 18 to 25, according to DI Marketing
In addition, We Are Social data cited earlier found that Zalo and Facebook Messenger had the same install rate, 25%, among smartphone users in Vietnam as of Q4 2015 Zalo has benefitted from a lack of strong competition from regional messaging platforms like Line and Kakao Talk This is partly due to resistance among consumers
to digital payment systems In underbanked Vietnam, consumers still rely on cash to pay for most goods and services While Facebook generates its revenues largely through advertising, platforms like Line and Kakao Talk are heavily reliant on in-app purchases made using digital payment systems, which are not yet widely adopted
in Vietnam
The use of messaging apps in Vietnam is not a zero-sum game, with a majority of end-users installing a number of apps that provide essentially the same service According
to DI Marketing, 89% of messaging app users in Vietnam used more than one messaging app
Trang 7% of respondents
Number of Messaging Apps Used by Smartphone
Messaging App Users in Vietnam, by Age, June 2016
18-25
26-30
30-35
35+
Total
Note: n=1,200; via smartphone; numbers may not add up to 100% due to
rounding
Source: DI Marketing, "Chat Apps Usage in Vietnam," June 10, 2016
212097 www.e Marketer.com
The market for messaging apps was most fragmented at
the younger end, with 45% of respondents ages 18 to 25
using four or more messaging apps In fact, the research
showed that those under 35 were using only one app in
significantly smaller numbers than those who were 35
or older
LOCAL AND REGIONAL PLAYERS RULE ECOMMERCE
Ecommerce has yet to take off in Vietnam eMarketer anticipates retail ecommerce sales, excluding travel, will total $1.71 billion in 2016, accounting for only 1.1% of the $161.16 billion in total retail sales
Retail ecommerce sales in Vietnam will total
$3.26 billion by 2020, constituting 1.5% of all retail sales, eMarketer estimates
billions, % change and % of total retail sales
Total Retail and Retail Ecommerce* Sales in Vietnam, 2015-2020
Total retail sales
—% change
Retail ecommerce*
sales
—% change
—% of total retail sales
2015
$147.99
9.9%
$1.37
43.5%
0.9%
2016
$161.16
8.9%
$1.71
24.3%
1.1%
2017
$174.37
8.2%
$2.08
22.0%
1.2%
2018
$187.45
7.5%
$2.47
18.5%
1.3%
2019
$200.57
7.0%
$2.88
16.8%
1.4%
2020
$213.61
6.5%
$3.26
13.2% 1.5%
Note: converted at the exchange rate of US$1=VND21,913.7; excludes travel and event tickets; *includes products or services ordered using the internet via any device, regardless of the method of payment or fulfillment Source: eMarketer, Aug 2016
213220 www.e Marketer.com
VECITA reported that ecommerce revenue in 2015 had totaled $4.07 billion, an increase of 37% from the previous year
The country’s ecommerce landscape is dominated by local and regional players Lazada Vietnam, which is majority-owned by China’s Alibaba Group and carries its own inventory and serves as a marketplace, ranks among the top players in the country According to SimilarWeb, Lazada Vietnam recorded the highest number of monthly page views in Vietnam in August 2016 at 24.5 million That put it ahead of consumer electronics retailer The Gioi Di Dong, business-to-consumer (B2C) platform Tiki.vn, online retailer Sendo.vn and several others
Trang 8Leading B2C Ecommerce Sites in Vietnam, Ranked by
Monthly Page Views, Aug 2016
Vatgia.com 10.4
Fptshop 7.7
Hotdeal
3.2
Nguyenkim.com
3.2
Lozi 2.4
Phongvu
1.5
Note: represents activity tracked by SimilarWeb, broader industry metrics
may vary
Source: SimilarWeb as cited by ecommerceIQ, Sep 27, 2016
217789 www.e Marketer.com
According to data from DI Marketing, advanced handsets
have still not yet displaced desktops and laptops Its
August 2016 survey of digital buyers in Vietnam found
that 75% of respondents used a PC to make a purchase,
while 51% used a smartphone and 21% used a tablet
% of respondents
Devices Used for Digital Purchases by Digital Buyers
in Vietnam, Aug 2016
Tablet 21%
Note: n=565
Source: DI Marketing, "Study About Online Shopping Behavior in Vietnam,"
Sep 12, 2016
216713 www.e Marketer.com
However, there are signs that advanced handsets are
making inroads among digital buyers in Vietnam Tran Hai
Linh, CEO of Sendo.vn, said in June 2016 that 75% of its
customers accessed the site by smartphone
The growth of mcommerce in Vietnam is also in line with
wider regional trends Online marketing services provider
Criteo found that mobile transactions made up 54% of all
digital ecommerce transactions in Southeast Asia in Q2
2016, an increase from 39% in Q4 2015
VECITA found that 64% of digital buyers in Vietnam had
purchased soft goods and cosmetics digitally in 2015,
making them the most popular product category for
ecommerce Consumer electronics ranked second (56%),
followed by kitchen and other home appliances (49%)
% of respondents
Product/Service Categories Purchased Digitally by Digital Buyers in Vietnam, 2015
Clothing, shoes, cosmetics
64% Tech/electronics
56% Kitchen and home appliances
49%
Books, stationery, gifts, flowers
42%
Travel (airfare, train ticket)
34%
Food
33%
Movie or concert tickets
22%
Hotel bookings, tours
19%
Education/business services 7%
Music/videos/DVDs/games 7%
Spa and beauty services 6%
Other 2%
Note: ages 15-49 Source: Vietnam Ecommerce and Information Technology Agency (VECITA),
"2015 Vietnam Ecommerce Report," April 15, 2016
210032 www.e Marketer.com
DIGITAL BUYERS ATTACHED TO CASH
ON DELIVERY
In Vietnam, cash on delivery (COD) remains a favored payment method among consumers, especially in urban areas
According to a July 2016 survey of digital buyers living in urban Vietnam conducted by Q&Me, 85% of respondents used COD as their main payment method for digital purchases Bank transfers were the primary payment method for 8% of those polled, while only 6% said they relied on debit or credit cards, a reflection of the low penetration rate of payment cards in the country
Trang 9% of respondents
Primary Payment Method Used for Digital Purchases
According to Digital Buyers in Urban Vietnam*,
July 2016
Cash on delivery 85%
Bank
transfer
8%
Credit card/
debit card 6%
Note: numbers may not add up to 100% due to rounding; *Hanoi and Ho
Chi Minh City
Source: Q&Me, "Vietnam Ecommerce Market Survey," July 19, 2016
214693 www.e Marketer.com
Similarly, VECITA reported that 91% of digital buyers in
Vietnam had used COD to complete an ecommerce
transaction in 2015, an increase from 64% in 2014 Digital
buyers’ use of ewallets actually declined from 37% to
11% over the same time period, while bank transfers
were used by 48% of buyers in 2015, up from 14% the
year before
% of respondents
Payment Methods Used for Ecommerce Transactions
According to Digital Buyers in Vietnam, 2014 & 2015
Cash on delivery
64%
91%
Ewallet
37%
11%
Bank transfer
14%
48%
Scratch cards
11%
6%
Payment card (credit, debit, gift, etc.)
7%
20%
Other
1%
1%
Note: ages 15-49
Source: Vietnam Ecommerce and Information Technology Agency (VECITA),
"2015 Vietnam Ecommerce Report," April 15, 2016
210079 www.e Marketer.com
Vietnam is similar to India in its adherence to COD as a preferred payment method As in India, consumers have little incentive to switch over to other payment methods, with many services accepting cash as a matter of course
“Even if I want to pay my electricity bill, someone comes around and collects cash,” said Richard Burrage, managing partner at Vietnam-based market research firm Cimigo Furthermore, COD also makes it easier to refuse
an order once it arrives “If I do some shopping online, I’ll pay them in cash All of the fears of online shopping are dispersed; if I don’t like it, I can turn it away,” said Burrage The ability of consumers to inspect goods purchased online before paying has alleviated some of the trust issues related to the nascent ecommerce market in Vietnam, but it has also provided an incentive for vendors and third-party logistics providers to keep the cost of COD free or low And when costs related to COD purchases are incurred, they are usually shouldered by the merchant
In addition, merchants and consumers prefer cash payments because it’s easier for such transactions to remain off the books, thus avoiding taxes
Bank cards are rarely used to buy goods or services thanks to the combination of an underbanked populace and a dearth of point-of-sale (POS) terminals for offline purchases The government in Vietnam has moved in recent years to encourage consumers to move toward payment methods other than cash by establishing new regulations for digital payments
Still, much work remains to be done if vendors are going
to start accepting more payment methods According to
a November 2015 survey of businesses in Vietnam by the Vietnam Ecommerce Association (VECOM), nearly all (97%) respondents accepted bank transfers, while only 16% accepted payment cards, a category that included credit and debit cards Only 4% accepted digital wallets
% of respondents
Noncash Payment Methods Accepted by Businesses
in Vietnam, Nov 2015
Payment card*
16%
Digital wallet 4%
Scratch card**
2%
Note: n=4,735; *includes all types of payment cards (credit, debit, gift, etc.);
**type of preloaded payment card Source: Vietnam Ecommerce Association (VECOM), "Viet Nam E-Business
Trang 10The digital wallet sector in Vietnam remains fractured
Online newspaper VietnamNet reported in August 2016
that there were 16 digital wallets in operation in the
country as of May 2016, but many of them had been
developed by ecommerce platforms and worked solely on
those websites In order for digital payment methods like
mobile wallets to catch on in Vietnam, they will have to
provide a greater range of service options for consumers
PAYING CUSTOMERS STILL PREFER CABLE AND SATELLITE OVER VIDEO-ON-DEMAND
Despite the emergence of various video-on-demand (VOD) platforms in Vietnam, paying for online video services has not yet become a widespread behavior among consumers there
A September 2015 poll of internet users in the country conducted by Nielsen found that only 13% of respondents paid for an online video service provider Cable TV remained the dominant mode of pay TV, used by 78%, while 40% paid for satellite TV
% of respondents
Internet Users in Vietnam Who Currently Pay for Select TV/Video Services, Sep 2015
Satellite provider 40%
Online service provider 13%
Other 7%
None of these 4%
Source: Nielsen, "Global Video-on-Demand Survey" as cited in press release, March 18, 2016
210113 www.e Marketer.com
Despite the uphill battle online video services face from traditional TV platforms, digitally savvy consumers are turning to online resources in search of more and different programming, as well as the freedom offered
by on-demand services, according to data from Nielsen’s November 2015 study
“Consumers are exercising their choice of how, when and where they can obtain their content and are more active
in their media habits than ever before,” said Doan Duy Khoa, director of consumer insights for Nielsen Vietnam