There is a quite a nice one at Grand Corpthorn WaterFront located beside Zouk. The buffet is located at the restaurant in the lobby. The international buffet comes together with a thematic main course; on different day you get different types of mains like steak day, japanese food day, bbq day... etc.
Quite a nice one ... 30 plus. The last time i tried was about a year back so you'd need to double check whether its still there.