If you want trade thai stocks, there are many brokage
firms that are registered with stock exchange of thailand,
and you can find all of them within their site links of brokers:
http://www.set.or.th
You may contact amreican broker "Paul renuad" who
owns website
http://www.thaistocks.com who now
reside in pukhet island for sometime. He offer monthly
subscribtion for his daily recommandation, and he might
give you the exact answer you looking for.
I guess you can directly can register with S.E.T also.
Since i live in thailand half a year, had heard from many
peolpe that trading gurues munipulate thai stock daily.
By the way why you want to trade thai stock, i have moved
here recently and do not intend to trade thai stock, since
i cant speak thai lanugage yet, and because of that i might
get cheated or make a mistake.