The Dângrêk Mountains (; , ; , ), also the Dângrêk Range, is a mountain range forming a natural border between Cambodia and Thailand. Geography Despite the length of the range, the Dângrêk are a relatively low mountain system, the average elevation of the summits being around 500 m. The highest peak is Phu Khi Suk (), an inconspicuous 753 metres at the eastern end, in the Chong Bok (603 m) area, where the borders of Thailand, Laos, and Cambodia intersect. Other summits are Phu Khok Yai (693 m), Phu Chep Thong (692 m), Phu Tangok (689 m), Phalan Sun (670 m), Phanom Ai Nak (638 m), Phanom Thaban (582 m) and 374 m high Khao Banthat (เขาบรรทัด) at the western end. The northern side of the Dângrêk Mountains is gently sloping, while the sides facing south are usually a steep escarpment that dominates the plain of northern Cambodia. The watershed along the escarpment in general terms marks the boundary between Thailand and Cambodia; however, there are exceptions. The main road connecting the two countries in this area cuts through a pass in the Dângrêk Mountains at O Smach. A small administrative division of Thailand in Surin Province, Phanom Dong Rak District, bears the name of this mountain range. Geology The mountains are formed mainly of massive sandstone with slate and silt. A few characteristic basalt hills such as Dong Chan Yai (293 m) and Dong Chan Noi (290 m) are found on the northern side of the mountain chain in Ubon Ratchathani Province. Ecology The Dângrêk Mountain range is mostly covered by dry evergreen forest, mixed dipterocarp forest, and deciduous dipterocarp forest. Tree species like Pterocarpus macrocarpus, Shorea siamensis and Xylia xylocarpa var. kerrii dominate. There has been much illegal logging both on the Thai as well as on the Cambodian side, leaving large hill stretches denuded, vulnerable tree species such as Dalbergia cochinchinensis have also been affected. Forest fires are also common in the hills during the dry season. There is not much wildlife left in the Dângrêk Mountains. Wild hog, deer, barking deer, rabbit, squirrel, gibbon and civet are some of the animals to be found in the areas where there has been no habitat loss due to human encroachment. Among the endangered species, the white-winged duck deserves mention. The Phanom Dong Rak Wildlife Sanctuary is a protected area in the area of the range in Sisaket