This year will be my 50th anniversary here in Thailand, and I have long given the question of thermal comfort and air conditioning all the thought I can muster. I've lived Bangkok and up country, in wood houses, concrete houses, you name it. I have degrees from MIT and Imperial College and wrote a book on heat transfer and tropical architecture. To celebrate my anniversary here I am presenting my final conclusion herewith:
You don't need air conditioning in Thailand.
What you do need is two things:
1. A domestic envelope that has high thermal mass like several inches of masonry and is completely shielded from the direct sun. This will reach a temperature equal to the mean air temperature, about 30.5 degrees in this month of April (87 deg F). For example, a fully sun-shielded condo such as the one where I am now.
2. A small table fan like the Hatari that is 3 feet from me as I write this.
This is perfectly adequate for Thais and will be for you too once you accomodate to it, a few weeks with the right attitude. Accomodation is the key to a happy life here.