Tham Lot (length 1,666m) is a cave system near Soppong, Pang Mapha district, Mae Hong Son Province, northern Thailand. The Nam Lang River flows through the cave which is filled with stalactites and stalagmites. The cave is also home to large numbers of bats and swifts. In Tham Lot and other caves nearby teakwood coffins have been discovered which are thought to have been carved by the Lawa tribespeople thousands of years ago.
Another cave in the area, the second longest known cave in Thailand, is Tham Mae Lana, which is 12 kilometres long. This was explored by Australian expeditions between 1984 and 1986. Other caves in the area which are over 1 km long include Tham Nam Lang (8,550m), Tham Bung Hu (4,442m), Tham Pha Mon (4,050m), Tham Seua/Tham Lom (3,100m), Tham Susa (2,617m), Tham Huai Kun (1,747m), Tham Pang Kham (1,370m) and Tham Plah (1,365m). Spirit Well (Nam Bua Phi), a spectacular large collapse doline and one of the largest known natural holes in Thailand, is south of the H1095 road. It is more than 200m across and 90 to 130m deep. It was first descended, by the Australians, in 1985.