Mae Yen waterfall is the best and most accessible waterfall to reach on foot from Pai town.
Head east over the road bridge and take the second left (just after Fluid). The first couple of kilometres are along a pretty lane past resorts and paddy, with fine views back across the Pai Valley, until the sealed road runs out and a footpath continues up a scenic, narrow valley lined with wooded hills. The total distance is around seven kilometres, and it's relatively easygoing though the path crisscrosses the Mae Yen stream numerous times, so it can depend upon water levels. The waterfall isn’t spectacular but the hike and scenery are very pleasant (the picture here is of the route along the way). Allow four hours or so for the round trip.
Other than for Mae Yen, you're really going to need transport to get to the few other waterfalls around. Most are quite pretty, though none really spectacular -- any guesthouse will provide directions.
Mor Paeng is a popular one and well indicated. To get here, follow the road past Santichong Chinese village, turn left after the Lisu village of Mor Paeng and continue to the end of the tarmac, from where it's a short walk away.
Less visited, but signposted, Pam Bok waterfall is reached by turning right just past Coffee In Love on the road out of town towards Chiang Mai.
By Mark Ord.