About 30 to 40 kilometers outside Chiang Mai, especially towards the north, there are quite a few programs offering more active trips: rafting, trekking, and often combination tours. With the rise of conscious tourists, more and more organizations also offer visits to elephant sanctuaries with a 'hands-off policy'.
You can easily book more tours, especially combination tours, via Get Your Guide.
Here are a few websites that organize these kinds of activities: