The Huai Kha Khaeng Wildlife Sanctuary is located in Uthai Thani and Tak Provinces, Thailand. The park was established in 1974, and is part of the largest intact seasonal tropical forest complex in Mainland Southeast Asia. It, coupled with the Thungyai Naresuan Wildlife Sanctuary was declared a World Heritage Site by the United Nations in 1991. Together, the two sanctuaries occupy 622,200 hectares. As of 2014 it still contained viable populations of large mammals, including gibbons, bears, elephants and Indochinese tigers, although like all other sites in mainland Southeast Asia, some species (e.g., rhinoceroses) have disappeared or have experienced severe declines.
Inside the sanctuary at the park HQ is a memorial to Sueb Nakhasathian and the cabin which he used. His story is moving, relating to the fact that in life, he and his team failed to stem the poaching of endangered wildlife. However only after his death from suicide did the issue receive due attention from the authorities. Today the sanctuary is a protected area recognised by UNESCO as an area of natural importance.

Source: Wikipedia, Site visit