I was very pleased with the Crowne Plaza Bangkok Lumpini Park. It doesn't have the type of stuff you will find at the really good sunday brunches at the higher end properties in BKK but I like it because it scores well on variety with Japanese, thai and western style dishes, freshness and service is very good. I also like the dining area which is very comfortable and not too busy like a lot of the other buffets.
I have some photos of the breakfast buffet in this review.
http://www.flyertalk.com/forum/inter...pini-park.html