The operation involved 50 officials from the Phaya Sua taskforce and the Department of National Parks, Wildlife and Plant Conservation’s land-plot inspection team.

Phaya Sua head Chaiwat Limlikhit-aksorn said the area inspected was used for agriculture purposes until 2002 but had been sold and passed through many hands until the latest inspection found it was now occupied by the two resorts.

He said officials would gather evidences to file a police.

Thap Lan National Park is part of the Dong Phaya Yen-Khao Yai Forest Complex, which is a natural World Heritage Site.

The 1.4-million rai (224,000 hectares) national park – Thailand’s second largest – has been extensively encroached upon by popular resorts, many of them owned by influential figures.