Can someone inform me re buying a prepaid sim card in SE Asia with Wifi? I'll be in Thailand, Myanmar, Cambodia, Vietnam and Laos with an Android

To save on calls you would ideally need a new sim card for each country you are visiting. For Thailand I like AIS prepaid sim cards as they have the best coverage throughout the country.

http://www.ais.co.th/12call/en/promotion.html

mobal.com if you must be in all thosecountries way better than buying SIM cards for each. Skype works best for me
All upscale hotels have wifi usually free worksgreat for me.
Buy trip cover and be careful with any expensive electronics you bring especially apple.com products they are theft magnets.

qwovadis - why do you say mobal.com is better than buying individual sims in each of the country the OP is visiting? Are you getting paid for promoting certain web site?

As an example using Thailand for comparison:

SIM cost from mobal SIM = $9 or 96 Thai Baht. AIS = $3.20 or 99 Thai Baht

mobal.com world SIM - incoming calls both local and from international numbers = $1.25 per minute or roughly 38 Thai Baht per minute. AIS = 0 Thai Baht per minute.

mobal.com world SIM - calling local numbers = $1.50 per minute or roughly 46 Thai Baht per minute. AIS = $0.29 or 9 Thai Baht per minute.

Erata - for the last comparison it should read:

mobal.com world SIM - calling local numbers = $1.50 per minute or roughly 46 Thai Baht per minute. AIS = $0.05 or 1.5 Thai Baht per minute.

and...

mobal.com world SIM - calling the USA = $1.95 per minute or roughly 60.45 Thai Baht per minute. AIS = $0.29 or 9 Thai Baht per minute.

In my experience so far, pre-paid SIM cards don't come with wi-fi. They may allow data access, but they don't provide access to any wi-fi data points. In Cambodia, you'll find free wi-fi in virtually every cafe, and most restaurants. The one time I purchased a SIM card in Cambodia, it proved completely useless, as I was never able to access any data service, despite the promises of the counter that sold it to me.

Prepay SIM with Wifi for Thailand: http://truemove.com/en/prepay-hispeed-net-sim.htm

IMO for Thailand "True" is only good for the major cities but their Wifi coverage is very good inside the Bangkok.