The recorded sightings of the 18 tigers were the joint effort of the Department of National Parks, Wildlife and Plants Conservation, the Freeland Foundation and the Panthera Foundation.
Dr Songtham Sooksawang, director of National Parks Office, told a press conference on Tuesday that recorded sightings of the tigers were a testimony of the pristine and rich condition of natural resources and ecological system of the Dong Phaya Yen-Khao Yai world heritage site and the effectiveness of forest patrolling by forest rangers.
The last time that tigers were caught by surveillance cameras of Wild Aid Foundation and Wildlife Conservation Society in Khao Yai national park was in 2002.
Tiger population survey was conducted last year by the department in cooperation with the two aforementioned foundations with altogether 158 cameras being installed in areas believed to be the habitat and feeding grounds of tigers in the world heritage site.
Dr Songtham said it was necessary not to disclose the sites where tigers were photographed in order to protect the big cats from poachers.
Tigers are regarded as endangered species with about 4,000 tigers worldwide, including between 150-200 in the western forest complex.