Mafia preying on popular islands are facing crackdowns as the government plans to wipe out elements reaping profits from unregulated businesses, starting with those on Koh Samet in Rayong.
"Koh Samet has some of the most serious problems such as rubbish and sewage management, influential thugs and so on," said Thanya Netithammakun, director- general of the National Parks, Wildlife and Plant Conservation Department.
"Several other islands and national parks have similar problems such as Lipe archipelago, Tarutao National Marine Park and Koh Chang. And they too will face similar legal action."
The government aims to make Koh Samet a high-quality tourist destination by restoring its natural beauty damaged by tourism businesses, he said.
The crackdown has started and received cooperation from Rayong provincial administration agencies, the military and police.
A former head of Khao Laem Ya-Mu Koh Samet National Park is facing an investigation led by Natthaphol Rattanaphan, director of the department's office overseeing national marine parks, after it was found that five of seven piers on Koh Samet were exploited by mafia groups.
The gangs would send their members to piers to collect money from tourists. About 60% was handed over to corrupt park officials and the rest to the gangs, according to Mr Natthaphol.
"The chronic problems on Koh Samet have gone on for too long," said Mr Thanya.
Mr Natthaphol said some business operators on the island have begun complaining about the government's "rigid" action, which they said hurt commerce.
He said officials have been told to take care to prevent those trading honestly from being affected.
Mr Natthaphol said some business operators had phoned him to air their complaints. They included retiring civil servants who had taken out loans and invested heavily.
They had mainly invested in paraglider and water scooter rental services that needed to be regulated, he said.
"Everything on the island must be made legal," he said, adding the popular blazing drum dances must be banned because they spill petrol on beaches.
Out of nearly 200 speedboats operating to and from Koh Samet every day, most are operating without a licence, Mr Natthaphol said.
All piers except the one managed by the Rayong provincial administration organisation will be dismantled. The department will build a single pier to receive tourists and collect docking fees.
Phitsanu Khemaphan, president of the association of business operators on Koh Samet, said the mafia-style groups were people in uniform and state agencies probably had better information about them than the association does.
He said a single pier would lead to congestion as boats arrived at the same time.