The owner of Phornphailin Riverside resort, beside Vajiralongkorn Dam, has refused to demolish the buildings, which were found to be within the boundary of Khao Laem National Park, reports the Bangkok Post.
Meanwhile, the owner of another resort on Thursday demolished four buildings found to also be inside the park, in Thong Pha Phum district.
Nipon Chamnongsirisak, the director of Protected Area Regional Office 3 (Ban Pong), and Khao Laem National Park director Tewin Meesap led a team to Krathom Rim Than resort in tambon Chalae of Thong Pha Phum district.
The park earlier issued an order for the resort owner, Saman Hong-iam, 42, to demolish all four structures within 30 days, or be liable to up to 3 years in prison and/or fine of B300,000, plus the demolition cost of 60,000.
Mr Saman on Thursday complied with the order, removing all four structures.
Authorities then sent trucks and crews to clear the land and prepare it for forest restoration.
Mr Nipon and Mr Tewin later went to Sangkhla Buri police station to file a complaint against Nathisinee Tengthiang, the owner of Phornphailin Riverside resort.
The park issued an order on Sept 1 for Ms Nathisinee to demolish the structures within 30 days, a second warning on Oct 2 giving her 15 days, and a final notice on Nov 24, giving her seven days.
Ms Nathisinee refused to comply with the orders.
Mr Nipon said the resort owner would face charges for refusing to demolish the structures. She would be liable to a jail term of up to three years and/or fine of B300,000, and a daily fine of B10,000 a day until the demolition was complete.
Officials would demolish the resort, and the owner would have to pay the cost, B1.2 million, Mr Nipon said.