The owner of the Saiyok Floatel has been given 30 days to remove all floating structures from the Kwae Noi River because the resort is encroaching on Sai Yok National Park in Kanchanaburi.
Park authorities posted the order by the Department of National Parks, Wildlife and Plant Conservation at the 20-million-baht raft resort on Friday.
If the owner fails to comply within 30 days of the order, park authorities will remove the structures and charge him 500,000 baht for the work.
The owner, identified as Wasant Sodsai, faces fines of up to 10,000 baht a day for failing to comply with the demolition directive. That is in addition to a maximum fine of 50,000 baht and/or six months in jail for having illegal structures in a national park.
Niphon Chamnongsirisak, chief of the Protected Area Regional Office 3, said he hoped Mr Wasant would comply with the order and warned of legal action if he does not.
Authorities were acting on a ruling issued on May 24 by the Central Administrative Court, which found the resort was located on national park land in Sai Yok district. Mr Wasant decided not to appeal the ruling to the Supreme Administrative Court.
Mr Wasant had earlier faced potential criminal charges filed by the park with Sai Yok police. But prosecutors in Kanchanaburi decided in August 2018 not to indict him, saying he had no intention to encroach on public land.