My 3rd stay at Noble Nights when visiting Kanchanaburi. It's a good compromise between a basic B&B and a much more expensive hotel. The rooms are comfortable enough, with all the basic facilities you need, including a room safe & free wi-fi. The small, open air bar & lounge (which also serves food), is a great place to return to after a hot day exploring the area, as is the swimming pool. For the evening, you are on a street filled with bars and restaurants of all kinds, where the prices are much, much cheaper than you will find in the more mainstream tourist centres of Thailand.
A great place to spend a few days unwinding in the tropics. Tip: If coming by taxi, make sure you have the hotel's phone number so you can give this to the taxi driver when you get close, so he can establish exactly where the hotel is - it's easy to miss it.