Nature Expeditions

Thailand’s jungles are teeming with wildlife, including tigers, elephants and thousands of bird species. Though wild, these areas are more accessible than one might think, and treks to hilltribe villages have grown in popularity.
Soft AdventureAnyone with a love of the great outdoors will enjoy the lush mountain trails of northern Thailand. Organized treks are widely available from agents in Chiang Mai, Chiang Rai, Mae Hong Son and smaller towns such as Mae Sot, Pai and Mae Sariang. These take you through remote villages, where you stay overnight with ethnic hill tribes such as the Lahu, Lisu, Akha and Karen. Average treks are 4 days, 3 nights and cost around US$50, but longer treks are possible. Many treks include bamboo rafting and elephant riding, although these may cost extra. Always ask what is included before paying for a trek - shop around and ask for recommendations. Your trekking agent and their guides should also be registered with the government.
Some Don'tsHill tribe villagers are generally very hospitable and friendly, but you should take care not to offend their sensibilities. Always ask before taking photographs of people and homes, and show respect for their religious beliefs, items and ceremonies. Avoid the temptation to shower candies and other gifts on children, as this can create certain expectancies when other trekkers come through. Guides can mediate to arrange donations for the community if you want to give.
TrekkingThe best time to go trekking is during the dry season, from September/October to January/early February. Nights are chilly around Christmas and New Year, so take warm clothing. You can go trekking at other times, but February to June/July is hot, and it rains heavily from July to September.
Reference : http://www.circleofasia.com/Nature-Expeditions-Thailand.htm