Op Khan is a national park in Samoeng District that covers the area of mountainous limestones, lush forest and freshwater sources of 484 square meters. Its tallest peak is Yod Khun Thian, which reaches the height of 1,550 meters above sea level. Op Khan is the only place in Thailand that finds a kind of rare wild orchid named ‘Ueang Manee Tri Rong’ (Dendrobium wardianum Warner) that features scented smell. is found only in this area of Thailand. The tri-colored orchid blossoms during the month of January every year.
The park is home to numerous kinds of wild animals, from civets to bears, as well as natural attractions such as a Grand-Canyon-like Op Khan Gorge on the banks of Mae Khan River, s shallow-water swimming spot of Huai Ya Si and Huai Pong, Pha Toob that features interesting-shaped cliffs, Mae Tian Waterfall, Mae To hot springs and Than Takkatan (grasshopper cave) that houses stalactites and stalagmites.