This Tunnel is situated in Khao Nam Khang, Mu 1, Tambon Khlong Kwang, approximately 4 kilometers from the Park Office. Once known as the Piyamit Village 5, the tunnel was operated by Communist insurgents. After almost 40 years of fighting with the Thai Government, the Communist Party was dispersed and became part of Thai Development Participants in 1987.
Thailands largest and longest man-made tunnel, it was completed in two years with three separate corridors and three levels deep. The tunnel itself could accommodate about 200 persons with several rooms such as conference room, sick bay, radio transmission room, kitchen, firing range, etc.