Environmentalists and bird watchers have complained about "No Entry" signs along Khao Yai National Park's nature trails while park authorities insist they are to deter poachers, not nature lovers.
Philip D Round, regional representative of the Wetland Trust and co-author of A Guide to the Birds of Thailand, voiced his concern after finding signs that said "No Entry" or "Activity Prohibited in This Area" in the popular national park in Nakhon Ratchasima province.
The signs are posted along trails that used to be open to visitors keen on surveying nature along the routes, he said.
Such a prohibition is against the national park's principle of educating the public about nature, Mr Round said.
"Khao Yai is a World Heritage Site yet the impression it gives is that visitors are not welcome. Visitors are allowed to drive their cars through the park but they are no longer permitted or enabled to walk on most park trails," he said.
According to Mr Round, only a couple of trails are free of such signs.
The Bird Conservation Society of Thailand's Wicha Narungsri said the national park has prepared eight main trails for visitors. The authorities should provide a clear explanation to visitors if these areas are now restricted, he added.
He also called on park officers to improve the condition of the nature trails, many of which lack clear direction signs.
"Khao Yai National Park is an A-list park. There is an urgent need to make sure visitors go in the right direction. They need to ensure trekkers will not get lost in the forest," Mr Wicha said.
Krisada Homsud, chief of Khao Yai National Park, insisted that the six nature trails with restriction signs remain open to visitors.
Mr Krisada said the trail signs are part of an attempt to deter tree poachers. They will also help limit the number of people entering protected zones. He said the "Activity Prohibited" sign means the trail requires registration before entry as the route is complex. The information can be useful in case people go missing in the park.
Mr Round, however, said the reasons are unacceptable. "This has created difficulty for bird-watching groups and people who would like to study bird life in the forest. All we can do now is just watch birds along the road, which is no longer safe for us," he said.