Subject: Sumatra, Bali, Thailand
To me the south is beaches, as I said I haven't traveled much there. Most of the islands are crowded now, but Koh Tao and on the opposite side in the Gulf of Thailand Koh Chang were both nice.

The North consists of losts of territory. Take a look at a map and the places I mention will make more sense.I don't recall how much time you have. Chiang Mai is a major hub for lots of activities in the north and the city itself has lots of interesting temples, markets and crafts to explore. You can base yourself there if you wish and do day trips or so. I have a friend there that can help you coordinate it.You can go on a trek in the jungle, the more time you have the more remote an area you can go to. If you like ruins then to the east a stop in Sukothai should be on the list, once the capital of Siam over 700 years ago has spectacular ruins. One of the few areas I have found untouched and quiet is the picturesque Mae Hong Son to the west on the border of Burma. To the north east (a day trip) you can go to Chan Saen (ruins) and the famous/infamous Golden Triangle. While this has become touristy it still is interesting and if you go take a long tail boat ride on the Mekong River. You can way north to Mae Sai, the northern most point in Thailand (this is where I lived).Growing by the year, it's claim to fame is that it borders on Burma, depending the border is open and you can shop and wander within 1K on the Burmese side for a fee. You can probably hire a Burmese guide and go by motor bike.