While backpacking in Thailand, Kanchanaburi should be a mandatory stop. I would even call it a rite of passage. The Bridge on the River Kwai is great sightseeing, and there are plenty of places for an elephant trek if that's what you're into. The town of Kanchanburi is pretty much a backpacker's dream. Cheap bars, street food, and accomodation for $3 a night is what draws in the crowds of young people in tank tops, sandals, and questionable hygeine levels.
When exiting the bus station, tell any motorcycle taxi that you are going to the Jolly Frog and he will know exactly where it is. An easy 10 minutes from the station, the Jolly Frog has a large outside dining area with wifi and a check in desk. Don't expect great customer service while reserving your room, but with rates starting at just 80 baht (around $3), you get what you pay for.
A nicer room with AC and an en suite bathroom will run closer to $6-$7 per night. All the toilets are bucket flush, and definitely bring your own towels and toilet paper. The beds are lumpy and anyone squeamish should probably just drink more before crawling into bed because I can't promise the sheets are clean.
No matter which room you choose, the views are spectacular. Bring bug spray because all the water attracts mosquitos. The Jolly Frog isn't about finding a nice room or spending time in bed. It's the premier spot in Kanchanburi for meeting other backpackers, eating a plate of fried rice outside while using the wifi, and enjoying a couple Changs before a night out. All the money you end up saving on accomodation can easily be blown on smoothies, hangover food, or another tank top. But with a 10 baht bar ($.30) right down the street, you might just leave Kanchnaburi with some baht in your pockets!
Address: 28 soi China Mae Nam Khwae, Kanchanaburi 71000, Thailand
How to get there: From Bangkok, vans leave about every 30 minutes from Victory Monument