We've stayed at the Dusit Thani and the Lebua State Tower. Club rooms in both.
Dusit Thani was beautiful, very classy and upscale but in a slightly older genteel way. Looks closed at the moment.
Lebua was more modern. The roof bar is worth a visit for the sheer scale of the height although it is terrifyingly high, with glass walls. The actual hotel was nice enough but nothing too exciting. The breakfast was incredible though, one of the best we've had. Nowhere does 5 star breakfasts like the Thais, they are exceptional everywhere we've stayed.
We went to the buffet dinner at the Peninsula and it was excellent. When we went we did wish we'd been staying there.
We've been to Krabi, Kho Phi Phi, Koh Lanta, Phuket and Koh Samui. All amazing to visit but Koh Samui was quite expensive for hotels. We rented a villa and would highly recommend that, it was utterly beautiful and you can still a driver, chef etc.
Thai hospitality is amazing and on the whole the people there were absolutely lovely. Hope you have a great time.