National parks benefit society in many ways. Besides their ecological functions, national parks also provide recreational benefits to park visitors and help earn foreign exchange from international travellers. In Thailand, more than 80 forest reserves have been declared national parks under the National Park Act of 1961. However, despite the recreational benefits, many national parks in Thailand are currently threatened by various activities such as encroachment by local villagers, forest fire, soil erosion, human settlement inside the parks or pollution created by the villages inside the parks as well as by tourists. This cumulative negative impact on national parks may in part be attributed to insufficient funding for park management. Funds for park management comes from two sources the central government budget and revenue from park entrance fees. The central government budget allocated for park management has been limited as it competes with other development programmes, such as education, public health care, infrastructure or even military spending. With regard to entrance fees, it has been found that park revenue from entrance fees could be increased if national parks were priced appropriately. In the case of Khao Yai National Park, a study by TDRI/HIID found that the Willingness-To-Pay (WTP) for entrance fee is 22 baht while the Khao Yai National Park currently charges only 5 baht per visitor (Kaosa-ard, Patmasiriwat, Panayotou and Deshazo 1995). Besides, not only are many national parks under-priced, some (such as Doi Suthep) do not collect any entrance fee at all.