My friends and I stayed at a resort of floating huts on the river about 40 kilometers from Kanchanaburi in a town called Sai Yok. We negotiated the price, which included all meals, but alcohol was extra. We were left alone all day to do our own thing, and at meal time the owner returned and prepared the food. The menu choice was good and we were able to have three different dishes all of course with rice.
The experience was without doubt the best that I have had in Thailand. We stayed for 5 nights, initially by ourselves but after the first day others arrived, we all sang and drank and had a great time checking out the local attractions and markets for souvenirs. Tourist operators from Bangkok have daily trips or you can have a few days with accommodation, its up to you.
The whole area is fantastic, ---- don't think that the bridge, and museums are the only things of interest. There are several waterfalls, golfcourses, caves, fishing, rafting, elephants, and wild life parks, all within a short distance.
Do yourself a favor and stay a while and feel the beauty of Thailand, you will never forget the experience.