I haven't seen one really really great FFS result from dr. Chettawut, that doesn't mean there aren't a few, or a lot... based on the results from his website, and those which can be seen either on this or other websites/groups, I can't say I was really impressed with any result (I had a chance to see). I have seen couple really good results from dr. Suporn... and also a couple which were not so great. But then again, even dr. Spiegel has many results where patients end up with androgynous looking face, yet we can't really know for each case, if it is failed attempt at achieving convincing feminine apperance, or it was a patients personal request to have a result exactly like that (in-between).
Based on results available, I would say that Dr. Chettawut and Dr. Suporn are both good options, but I would also suggest looking outside of Thailand for other FFS options.