Authorities found a cluster of 147 plots of forest land in Loei's Dan Sai district have been encroached upon by a company linked to construction mogul Premchai Karnasuta, following a raid led by the Department of Special Investigation (DSI) on Tuesday.
Mr Premchai is the subject of a poaching probe that began in February.
The raid focused on Rang Yen Resort, which is owned by PCK International Co, DSI director-general Paisith Wongmuang said, adding that three of the company board members are relatives of Mr Premchai.
Pol Col Paisith said the Department of Lands had already annulled the Nor Sor 3 Kor titles for the 147 plots on July 31, after it found that the titles were issued unlawfully.
The titles covered 6,229 rai, but authorities believe the total forest area encroached upon may be as high as 10,000 rai.
He added that the annulment of the titles was done because the Sor Khor 1 documents used by the company to apply for the Nor Sor 3 Kor titles are actually linked to lands in neighbouring Phu Rua district.
Aerial pictures of the raided plots taken on Tuesday found that up to 10,000 rai of forest land had been encroached upon, said Pol Col Paisith.
Police have pressed land encroachment charges against three board members of PCK, and authorities will delve deeper to find the person who approved the fake documents when the request for the Nor Sor 3 Kor title deeds was made, he said.
The DSI also found drastic changes to the encroached plots, including a personal dam built across a creek that prevents water from flowing into a farmland area downstream, he said.
Col Phongphet Ketsupha, head of a team of Internal Security Operations Command (Isoc) officials that also took part in Tuesday's raid, said that villagers used to rely on water from Nam Duk creek to irrigate nearby dragon fruit plantations, before the company built the dam with metal sluice gates that have not been opened.
Pol Lt Col Prawut Wongsrinil, deputy chief of the DSI, said because the aerial pictures are three-dimensional with high resolution, they could be used as evidence to prove that PCK had encroached up to 10,000 rai of forest land.
