An illegal oil trade ring has threatened to kill reporters who have exposed its activity, according to the Press Association of Southern Thailand.
Customs officials seized 230,000 litres of petrol illegally smuggled off Phuket in July. The smuggled oil was worth 15 million baht.
Since the emergence of new reports on illegal oil trading in the southernmost region, the association has learned that the smugglers plan to raise funds to kill the journalists responsible, said association president Chaiyong Maneerungsakul.
The fresh publicity has prompted authorities to improve their efforts to clamp down on smuggling of petroleum from Malaysia, denting the illegal oil trade operation and angering those who profit from it.
The association has already asked Region 9 Police and the local military and administrative authorities to investigate the threat to journalists, Mr Chaiyong said.
The illegal oil trade is said to be a primary source of funding for the decade-old insurgency in southern Thailand. It has also been damaging the local economy, say authorities.
Oil smuggling activity to evade tax tends to rise and fall with world oil prices, but the fact that fuel is heavily subsidised and lightly taxed in Malaysia compared with Thailand makes smuggling a big problem in the South.
Some of the smuggling is on a small scale, involving cars with modified fuel tanks for example. But most of the activity takes place at sea.
Deputy Prime Minister Chalerm Yubamrung claimed in Parliament in August that some opposition politicians were major players in oil smuggling in the South but he gave no names.
Since the beginning of the latest crackdown, many illegal oil businesses have been shut down and smuggling operations have been greatly disrupted.
Police on Saturday stopped two illegal oil tankers carrying approximately 10,000 litres of gasoline and diesel fuel.
The first tanker was a modified fishing trawler 4.72 metres wide and 14.63 metres lon. It was stopped off the coast of Koh Yao in Muang district of Satun province.
On the ship, the police discovered 5,100 litres of diesel fuel. Its Malaysian crew could not produce proper documentation and were detained.
About an hour after the first bust in the same waters, another oil tanker disguised as fishing boat was halted. It measured 5.49 metres wide and 19.3 metres in length.
About 3,800 litres of gasoline were founded on board with equipment ready to offload its shipment.
Its three Thai crewmen, including Wichet Torawan, 38, were arrested and charged with smuggling after they failed to show importation paperwork.
The capture of both tankers was a part of an operation aimed to hamper the illegal oil trade. The shipments will now be processed by the Customs Department.
However, the authorities conceded that it is difficult to catch all smugglers as the activity is very lucrative, given the price differnce of 6-7 baht per litre between Malaysia and Thailand.