The answer to that question is to obtain a non-immigrant visa. Non Immigrant visa’s are issued at embassies outside of Thailand and are valid for a 90 day stay, this visa may be extended within Thailand for periods up to one year at a time. There are three basic grounds to obtaining and renewing Non Immigrant visa’s which are:
1. that you are employed & have a work permit in Thailand, or
2. that you have a Thai family/wife, or
3. that you are retired and can prove that you have an adequate pension or other financial means to support yourself.