Preetam Rai

I am often traveling in South East Asia so I keep a few SIM cards handy. Here is a list of prepaid Mobile internet services offered by mobile telcos in Cambodia, Indonesia, Malayasia, Thailand, Singapore and Vietnam

Cambodia

Cellcard offers a tourist 2.5 G SIM for short stay use. It costs 10$ and comes with 10$ worth of data usage. (The data rate is 1USD for 5 MB)

Indonesia (thanks Rezwan)

Indosat:

A new IM3 brand SIM costs between 10000Rp-20000Rps (Apx 1-2 USDs) including 5000Rp balance.


There is a Internet voucher which is sold in many outlets

Internet charges – toll based or volume based:

* Toll INTERNET = Rp 5000 voucher. Customers duration settings based & internet access for 45 seconds. So will be charged Rp 20, Toll INTERNET balance = Rp 4980.

* The volume of customers change settings based & Internet Access 1 Mb. So will be charged Rp 1100 (1100 Kb x Rp 1.1), SHG balance of voucher Toll INTERNET = Rp 3880.

http://www.indosat.com/Mentari/Mentari_Update/Voucher_Internet_Indosat

Tariff of XL:

http://www.xl.co.id/XLPascabayar/XLInternet/Tarifdanlayanan/PaketXLInternetInstan.aspx


Malaysia

Celcom Broadband Prepaid™

Pack at just RM25 with preloaded credit of RM20 and be among the 1st to enjoy:

The widest and fastest Mobile Internet Service in Malaysia so you can get more done wherever you are.? Hassle free access, with no registration needed.? Affordability from only RM20 per week with no fixed monthly charges.

Myanmar

Prepaid SIM card is available for 20 USD from mobile shops in bigger cities but there is no data.

The Phillipines

Thans Mike Aquino for .Ph info
The Philippines has two main prepaid line providers – Smart Buddy and Globe Prepaid. Both of them have data services, too. SIM data dongles like Smart Bro and Globe Tattoo are pretty cheap, and getting cheaper.

Singapore

Starhub Maxmobile Prepaid Card – Buy at 7/11 stores and mobie phone shops

Singtel has a pre-paid mobile but their Flash laden site, makes it difficult to search

M1 - You can buy M1's pre-paid data sim from M1 shop at Bugis Junction. $18 for 3 days unlimited mobile internet usage.

All three providers have a voice only SIM pre-paid SIM cards too. You need your passport for identification. Most mobile shops and kiosks will sell you these cards. 

Singapore also has a free island-wide wireless network - wireless.sg but you will need a mobile phone with singapore number to receive the passwords once you register for this network.

Thailand

I usually buy the one-2-call sim card from the 7/11 stores. http://www.12call.ais.co.th/en/Content/Simcard/simNetsim210.html

Vietnam

Most of the cafes and budget hotels offer wi-fi.

Thanks to Dave A who posted the following in comments

VIET NAM Vinaphone has 100mb for 50000vnd (about $3us)per 30 days
you have to enable gprs by texting GPRS ON to 888
after recieving confirmation text M50 ON to 888 and the data plan is activated and will deduct this amount every month. there are other plans with other activation codes, including an unlimited plan for i think 300000vnd but i dont know those codes.
i have been completely satisfied with the service, have had coverage everywhere in the mekong delta, even way out in the countryside, and quite often full 3G in cdecent sized towns.
hope this helps!