I went to Chiang Mai several years ago and bought tours from booths on the street. If I remember right they were under 1000/bt and they put me with other people. When we did the Golden Triangle tour and in the middle we were offered a seperate long boat ride up the Mekong. About 200/bt extra. Was worth it watching how they fish with nets, they also stopped on the Los side for a half hour. Went up to look at the big Casino from the river. A few people doing visa runs were on the trip, too.