The Navy yesterday intercepted five Vietnamese fishing trawlers and detained 30 crewmembers for allegedly operating illegally near Koh Kra off Nakhon Si Thammarat in the Gulf of Thailand.
Since September, 29 Vietnamese trawlers have been intercepted in Thai waters.
The five trawlers stopped yesterday were towed to Songkhla Naval Base in the morning.
The crew of one of the trawlers claimed the vessel had been registered through the Marine Department and produced documentation, said Naval Region 2 commander Vice Admiral Naris Prathumsuwan.
Naris said the crew claimed that they could avoid arrest by producing the document.
He said the authorities would want to know how the crew obtained it, if it were authentic. The vice admiral said the trawlers came from Kian Yang and Kamao in Vietnam.
The crewmembers face a legal action in accordance with the Immigration Act 1979 and the Act Governing the Right to Fish in Thai Fishery Waters 1939.