As far as hotels in Bangkok go, you can find some of the best hotels in the world. My favorites are by far the Peninsula, located on the Chao River and the Mandarin Oriental across from the Peninsula.
Both are luxury hotels, with wonderful rooms and restaurants. I did stay last time at the Shangri-La. The Oriental and Shangri-La hotels are located in the Old Farang Quarter.
On my next trip I want to move from the river inland and stay at the Sukhothai hotel, which I understand is really wonderful.
Other hotels getting great press and reviews include the design hotel SALA Rattanakosin, The Metropolitan by COMO known for its Nahm restaurant and the Arun Residence with six suites along the river. There is also The Siam Hotel and The Cabochon as other options.