The Royal River Hotel
This is a good hotel near the Krung Thon Bridge. Rooms are large, comfortable and clean. The deluxe rooms of this hotel have a big balcony with a nice view over the river. It is relaxed to splash into the pool after a hot day of temple tramping.
River Side Bangkok
This two-star hotel has 262 "superior" and "deluxe" rooms. Rooms are fully equipped with modern facilities and some include a room-service breakfast. Many of the rooms have a nice view over the Chao Phraya River.
Marriott Resort and Spa
The Mariott is one of the best hotels in Bangkok. Its off-central location is actually a downer, but it does bring a relaxed ambience that makes it feel like a resort hotel. Also, there are shuttle boats to BTS Saphan Taksin station, so you still get to downtown relatively quickly. Rooms are magnificent, there's a tranquil pool and a good breaskfast.
Ibrik Resort by the River
A luxury boutique resort with only three private double rooms. Each room is beautifully decorated in a chic style with modern white walls and wooden floors. Two of the rooms offer a view over the Chao Phraya River. It is a good way to escape the chaos of the city, yet it is only a 15-minute ferry ride to the Grand Palace. Breakfast included.
The Royal City Hotel
This is a decent hotel near Central Plaza Pinklao. Rooms are spacious, comfortable and clean, but also quite old, dark and uninspiring. Facilities are plentiful, including a pool, fitness and massage. The staff is really nice and helpful. There is not that much to do in the area though, except for the nearby 7-Eleven.
Millennium Hilton
Obviously a very luxury hotel at the Chao Phraya river, offering a working desk, living room, high-speed internet, two LCD televisions, jacuzzi, rain shower and pool. There's a shuttle boat to River City pier and BTS Saphan Taksin station.