Somphot Duangchantrasiri, head of the Khao Nang Rum wildlife research station, which runs a camera trapping project in Petchaburi's Kaeng Krachan National Park, said his team had found the tiger population in the park was on the decline.
In their most recent camera-trapping project between November last year and January this year, no images of tigers were recorded. Significantly less tiger activity was also documented compared to a similar exercise in 2002.
''It is a warning sign of the [declining] tiger population in the site,'' he said. ''Although we can't say for certain there are no tigers left in the park, their population is certainly under threat due to deforestation and poaching,'' Mr Somphot said.
The research team set up 47 cameras over an area of 500 sq km.
The cameras recorded images of around 30 mammal species including marbled cats, clouded leopards, golden cats and elephants. But they found no tigers.
Still, the team found traces of tiger activity at five spots in Panern Thung area and near Petchaburi River. They expected at least one of them to be a female tiger.
In the 2002 study, the team set up camera trapping equipment at 21 points - less than half the number of the recent study - and captured images of only four tigers.
Mr Somphot said a similar trend has been found in Kui Buri National Park in Prachuap Khiri Khan province.
In a recent survey conducted by the World Wide Fund for Nature (WWF), tiger population density in Kui Buri had decreased from 0.8 tigers per 100 sq km to 0.4.
''We might lose the tiger populations of two national parks if there are no effective measures taken to save them,'' Mr Somphot said.
''The situation is very complicated as there are more than 7,000 people living in Kaeng Krachan National Park.''
The tiger population in Huai Kha Khaeng Wildlife Sanctuary in Uthai Thani province has remained stable, while the number of tigers living in Mae Wong national park in Kamphaeng Phet province has increased, he said.
Ruangnapa Phoonjampa, chief of a WWF project to increase tiger populations in Mae Wong and Klong Lan national parks, said the two national parks are large enough to house more tigers.
She said the tiger population density in Haui Kha Khaeng wildlife sanctuary is 2.5 per 100 sq km. ''There is enough food and space for them in the two national parks. Moreover, there are no people living inside the parks,'' she said.
The tiger population density in Mae Wong National Park is just 0.75 per 100 sq km. A recent WWF survey found 10 mature tigers with two cubs moving around Mae Wong National Park, in addition to the more than 32 other endangered species.
The survey has been forwarded to the Office of Natural Resources and Environmental Policy and Planning, which studied the environmental impacts of the proposed Mae Wong Dam project.
Conservationists fear construction of the dam will destroy tiger habitats.
An adult tiger sets off a camera trap in the Tenasserim mountain range in 2001. FILE PHOTO