I've had the seafood lunch buffet at Lord Jim's. It was great. Though I'm sure it is expensive for most Thais, it felt like a bargain to me. I think it was something like THB 900 or THB 1000 per person.
In addition to a raw bar, there's a sushi bar with made to order maki and nigiri. There's a huge warm seafood station. There's also a very nice dessert presentation. Service, as you would expect is warm and gracious.
When making a reservation, request a window table.