Luang Prabang, Laos
Currently writing this on the plane to Thailand from Luang Prabang, having been to Vang Vieng just before hand.
Vang Vieng was awesome, ended up spending a bit of extra time there then expected after I came down with my first bout of travellers gastro for about 3 days. Vang Vieng is a little community essentially designed for the backpacker around its main attraction tubing.
There is plenty of other stuff to do such as caving, hiking, mountain bike riding and...