I don't know which has the absolute coolest average temperature but if you are looking for a place to live the answer is probably Chiang Mai which is much cooler than Bangkok and a great city.

I agree nice weather and some nice guys there too

I don't know which has the absolute coolest average temperature but if you are looking for a place to live the answer is probably Chiang Mai which is much cooler than Bangkok and a great city.

actually, i don't think that's true. if you look here

http://www.arcims.tmd.go.th/dailydata/DailyMaxTemp.php

then type in a typical hot season date like 140410, or any date in April, you can see pretty much all of north and Issan is bright red, i.e. in the 40's, whereas Bangkok and the south is in the mid to high 30's