I believe you will need a business visa to legally work here (I am a Thai national so I do not have that issue) and getting one isn't a trivial task, unfortunately.
I suspect that the OP is most likely working using a tourist visa. IANAL but it is likely not legal if caught, but if you can get away with it, more power to you.
http://www.mfa.go.th/main/en/services/123/15388-Non-Immigran...
I believe you will need a business visa to legally work here (I am a Thai national so I do not have that issue) and getting one isn't a trivial task, unfortunately.
I suspect that the OP is most likely working using a tourist visa. IANAL but it is likely not legal if caught, but if you can get away with it, more power to you.