We were in BKK last September. We had amazing, memorable dim sum at the China House in the Oriental. They have something called the China House dumpling (I think) which was amazing. The atmosphere is soothing, and the service was great.
Dinner at Lord Jim's was a wonderful experience, but more for the view and presentation. I would return, but the food wasn't particularly memorable.
We have always loved the Spice Market, but hadn't been for ten years. We returned in September, and were very pleased. The restaurant hasn't really changed, but was absolutely kept up, and the atmosphere was great. I recommend the lime juice as a great accompaniment to the food.