River Hotel comprises three buildings, one rather elderly and two quite new. I have stayed in both old and new, and the rooms are about the same -- clean, reasonable size, well-equipped, cable tv, fridge, all aircon. Prices are from around Baht 600 to 1,100 for rooms (as opposed to suites). Staff are friendly and helpful, but with very limited English. Free wifi throughout the complex.
Only downsides are the size (200+ rooms), which means there are tour groups coming and going, and the location, which is about 2km from the town center.
If you are staying in Nakhon Pathom city, I would think this is your best all-round bet.