National Park, Wildlife and Plant Conservation Department tourism chief Anuchaya Chamnankid said accommodation had been snapped up at all of the country's most popular national parks.
These included Doi Inthanon, Doi Suthep-Pui, Khoa Yai, Mu Koh Similan, Mu Koh Samet, Phu Kradung and Nam Nao.
'Even if tourists are told lodgings and campsites are no longer available, they refuse to cancel their trips', Ms Anuchaya said.'Forestry officials are concerned about the impact of tourists' vehicles on the park's eco-systems. We often get traffic jams in national parks at high tourist season', she said.