Ziplining

North of Chiang Mai, there are several zipline parks. You can book directly at the parks or via your hotel/hostel. Expect prices around 1500-2500 THB for a few hours of fun.

A popular one in the area is King Kong Zipline.

Other addresses:
Skyline Jungle Luge — named so because you can also tour a circuit through the jungle on a so-called Luge Kart.

Pong Yang Jungle Coaster & Zipline also has a kind of rollercoaster through the jungle; you can even stay overnight in a tent.

A complete overview of zipline tours can be found here.