Thai police have arrested 13 suspects after a drugs raid on a tug in Thailand.

The men on board the 163-gt Srimongkholsap (built 1968) jumped into the water in an attempt to flee police during the operation on Monday night at a pier in Bang Pakong, Chachoengsao, the Bangkok Post reported.

Two tonnes of crystal methamphetamine, also known as ice, were discovered in cardboard boxes on board the Thai-flag vessel.

Police said they believed the drugs were destined for the Philippines and Australia.

Marine and narcotics officers searched the seagoing ship at the TNS Bangpakong jetty at 21.30 local time.

They were acting on a tip-off about a drug smuggling operation, police added.

The suspects were all Thai nationals.

A total of 90 boxes were found in rooms below deck, sealed shut with black tape.

The crystal meth was in compressed packs and hidden in bags of dried fruit to conceal the smell, according to major general Pharitphong, commander of the marine police division.

He said investigators had learned that the traffickers were planning to transfer the drugs to other vessels once the tug was in international waters.

Investigations were continuing on Tuesday.

Equasis lists the owner of the vessel as J Jaingam of Bangkok. It could not be contacted.

No insurer or port state control inspections are listed for the ship.

Maritime drug seizures invariably involve cocaine found on bulkers and container ships, usually planted without the knowledge of the crew members.