This is my first posting but I've been scouring the site for some time now. I'm planning an extended trip to SE Asia for Dec. 2011-Oct 2012. I'll spend time in Thailand, Cambodia, Laos, Vietnam, Malaysia and Burma (probably not in that order). I have tons of questions, but my first is about weather. From what I can figure out, April is the hottest month in the region. Does anyone have any advice on where to spend April and not be miserably hot?
I'd say anywhere near a coast. In general you get a pleasant breeze then. Inland places become very hot and humid.
Alternatively you could seek out some high mountain areas but there aren't that many with a cool climate in the countries you mention. Only in Vietnam (Sapa & Dalat) but both are only good for a few days so not worth it to plan your whole trip around that.
Then again, it's not that bad. You'll survive and can have a great time anywhere you'll be. Perhaps you should just consider aircon rooms for that period if you can't deviate too much from your itinerary.
It'll be bloody hot in April/May - but it's not completely unbearable. As stated above, stick to the islands where you can enjoy the sea breeze (and a dip in the ocean) or in the highlands.
I travelled around that time a few years ago in Thailand and Cambodia, and was pretty much in Siem Reap that I remember as being the worst. It's inland, and it was stifling hot especially around the temples which are made of stone and held the heat! But we survived, and had an awesome time.
Spend your first 3 months 'on the move', then chill out in the islands in southern and east Thailand for 2 months during the hottest period before ramping up again for the rest of your trip - I guess that would be my suggestion.