The most famous water fall in Tak is, Namtok Thi Lo Su ( Thi Lo Su waterfall ) is located in the Umphang Wildlife Sanctuary, a UNESCO World Heritage site, which links with the Thung Yai Naresuan and Huay Kha Kaeng Reserves, as well as Khlong Lan and Mae Wong National Parks. Together, they form Thailand's largest wildlife haven and one of Southeast Asia's few virgin forest.

Thi Lo in the local language means waterfall and Su means loud, thus, Thi Lo Su means waterfall that makes a loud noise. This is due to its size and the intense flow of the stream. In Karen "Gaolian", "Thi Lo Su" means Black Waterfall. So the origin of the name is uncertain.

The biggest and the most beautiful waterfall in Thailand, Namtok Thi Lo Su is also considered the sixth biggest waterfall in the world. The waterfall itself originates from Huai Klotho, streaming along limestone cliffs at a breath of 500 meters, the height of 160-170 meters down to cascading tiers which are surrounded by intact natural forests. There is a cave behind the waterfall well worth exploring and several levels of pools for swimming.

Getting there, visitors can drive, note that vehicles can possibly reach the office only during November to April. In the rainy season. For those deciding to drive a 4WD vehicle, the distance is 47 kilometers from (from the city of Tak to Umphang is about 5 hour drive by car) Umphang to the wildlife sanctuary office. From there, visitors have to walk along the 1.8 kilometers self-guided forest trail which provides unrivaled natural scenery. Camping at the Wildlife Sanctuary Headquarters is allowed near the falls, especially during October through December, when the waterfall is at its most beautiful.
Visitors are advised to make enquiries with the TAT Office in Tak Province (Tel: 05 551 4341-3) regarding travel conditions and camping opportunities.

One can raft from above as well.