I get requests sometimes from people who are moving here and want help in finding housing. Here is some advice:
The best way to find condos is to google 'condos in bangkok'. You can ask a few friends whom you already know, to recommend any places they have lived in or know of someone who has a nice place already - but it is hard for them to help you if they have no idea on your budget requirements or personal preferences, or they are not in the business of real estate.
Another suggestion is to post your help and suggestions request on the InterNations Bangkok Forum thread, under the heading, 'Housing'. We have a few members who are professionals in helping others find housing, but some of them take a commission. Just google some places, and contact them yourself, you'll be fine.
You can stay in a cheap hotel for a few days when you first get here, until you have been able to view the apartments. Some people stay in a hotel a few days, stay in a service apartment two months, then finally find their long term rental or purchase. Don't sweat it too much, there are plenty of spaces at all different ranges in prices. And you can always move at the end of your lease.