The city of Kanchanaburi by the River Kwai is a very good choice for visiting. Many things to do, places to visit, and places to relax.

Visit the War Cemetary with 7000 headstones for allied soldiers who died during the building of 'The Death Railway' in WWII. Take a walk crossing the river on the historic Bridge on the River Kwai. Enjoy the beautiful landscapes along the river on a ride at the 'Death Railway'. Visit the beautiful Erawan Waterfalls 60 km north of Kanchanaburi and hike the seven steps of the waterfall, and have a swim in one of the ponds at the buttom of each step. visit the Tiger Temple 45 km from the city, and see how the monks are taking care of the tigers - and have a chance to have your picture taken.

Visit the night market by the railway station and make a good bargain, check the bars in the street with most of the guesthouses, and enjoy a wonderful meal at either one of the restaurants by the river promenade or the big night food market by the bus station at night time.

Many nice, clean, friendly and cheap guesthouses, and some good hotels and/or resorts.

Kanchanaburi is easy to reach by air/con bus from the southern bus terminal. Trip takes two hours, bus leaving every 15 minutes, price 115 Baht (make sure you are buying tickets at the blue counters - orange counters are NOT air/buses).

Take a look at this link for further information about Kanchanaburi, you may stay for at least two days - have a nice trip

Kanchanaburi-info.com: destination guide to Kanchanaburi Province, Thailand