Laos springs to mind as a great venue for such a trip, hop onto a tour boat at Houei Xay and spend a delightful couple of days cruising down the impressive Mekong River, depart the boat at Luang Prabang and spend a few days exploring this delightful town, completely Laos with a huge amount of French colonial influence, one of the most fascinating cities on earth from an architectural viewpoint. Hop on to a local bus and head for Vien Vieng, with its astounding natural beauty and great value trekking, kayaking and camping tours.
There are an incredible amount of such experiences to be found within Asia, making a fantastic destination for adventure tourists and backpackers.