The Thungyai Naresuan Wildlife Sanctuary and Huai Kha Khaeng Wildlife Sanctuary cover three provinces including Uthai Thani, Kanchanaburi and Tak provinces in western Thailand. At 622,200 hectares combined, they form the largest protected area in Southeast Asia, and were listed as a UNESCO World Heritage Site in 1991.
The Thung Yai Naresuan Wildlife Sanctuary is located at the western national border of Thailand to Burma, at the southern tip of the Dawna Range. It extends from the northeast of the Three Pagodas Pass Sangkhla Buri District in Kanchanaburi Province into Umphang District in Tak Province.
The area is predominantly mountainous and composed of various limestones interspersed with massive intrusions of granite and smaller outcrops of quartzite and schist. Altitudes range from 180 meters above sea level at the Vajiralongkorn Reservoir in the south of the sanctuary to its highest peak Khao Tai Pa reaches 1,811 meters.
Major rivers are the Mae Klong and the Mae Chan which originate in the Umphang Wildlife Sanctuary and conjoin in Thung Yai into the Upper Khwae Yai which feeds the Si Nakharin Reservoir. Various smaller rivers in the south and southwest feed the Vajiralongkorn Reservoir while in the northwestern part of the sanctuary the Mae Kasat and the Mae Suriya flow into Burma.
How to get there: There are 2 routes to the Huai Kha Khaeng Reserve:
First route is to enter through the reserve headquarters that is around 102 kilometers from the province. Take the Uthai Thani-Nong Chang road (Highway No. 333) past Amphoe Nong Chang to Highway No. 3438 (Nong Chang-Lan Sak) to Km. 53-54, then turn left onto a laterite road for about 14 kilometers.
Access through the Thungyai Reserve is harder, as the roads are poor. Take the route Thong Pha Phum-Sangkhla Buri near Huai Suea to Khli Ti Village, a distance of 42 km. After that, there is an intersection leading to the Wildlife Sanctuary Headquarters at Huai Song Thai another 40 km.