Tat Mok Waterfall is at 45 minutes at the north of Chiang Mai.
No need to walk for this waterfall (only 100 meters), there is a parking. The entrance is not free (see price under).
You can also go at the top of the waterfall.
Link and information:
Google map of the waterfall : https://goo.gl/maps/zFSLxonkJ7UH3Bt88