For whatever reason it *seems* like there's not much Thai food in Tokyo. If you are searching for some you might give Kaffir Lime a try.
I'm not Thai and I've never been to Thailand so I'm sure I don't know what real Thai food tastes like but I do know what Thai food is like in L.A. and Kaffir Lime brought back those memories.
It's not at all a fancy place. In fact it's not much above a fast food place even if you do sit down and order but if you need a Thai fix give it try.