Love the Shangri-La Bangkok. It's perfectly situated by the river, and since I was last there in 2000, it has only got better. The Next2 Bar by the river is a great place as the sun is going down, and for night drinks, and the food at the Cafe is superb. Thailand is the land of smiles, but service is on Thai time and a drinks order at the bar can take a while to get to you...
One of the best buffets going around. Stayed in a "normal" room which has a great bed (super king) and great bathroom.
The hotel has a river boat that will take you down to a local mall (RiverCity - not that nice) and it's a good short ride on the Chao Praya .
Sirocco and the Skybar is a short walk away (3 mins) and is well worth going to for a drink with a view.
The sky train is connected through a long internal walk, and that can get you around the city quickly.
Was there for a business conference with over 300 delegates, and it catered for us very well. All had a good time!