The Royal Thai Navy (RTN) has come under fire over the sinking of its warship as a House committee on military affairs prepares to grill Prime Minister and Defence Minister Prayut Chan-o-cha over the matter next week.

Prasert Chantararuangtong, an adviser to the committee, said that the panel will summon Gen Prayut as well as navy chief Adm Choengchai Chomchoengpaet to explain the matter next week.

Mr Prasert, also secretary-general of the Pheu Thai Party, said he wondered how well HTMS Sukhothai had been maintained before it sank on Sunday, adding that the navy had received regular budget allocations for the maintenance of the warship.

He also criticised the navy over a lack of safety standards on board the ship, as there were not enough life jackets to go around when the vessel capsized during a storm.

He questioned whether the weather conditions were taken into account before the ship set sail.

"If the conditions were terrible, why was going out to sea insisted upon? A ship at this level must have had a system to pump out any water, but when it listed, it capsized and sank easily," he said.

An adviser to a House committee studying and monitoring budget spending management asked for an investigation into the navy's budget spending on the maintenance of the warship.

Adm Choengchai admitted on Tuesday that there were not enough life jackets for crew members on the ship.

But he explained that before the ship sank, it took on board 15 marines and another 15 personnel to take part in a ceremony marking the anniversary of the death of the Prince of Chumphon, who is regarded as the "Father of the Thai Navy" in Chumphon.

"Since there were not enough life jackets for the extra 30 people on board, we tried to use other equipment to save those who had no life jackets," Adm Choengchai said, adding a life raft can accommodate up to 15 people.

"Of the 30 who had no life jackets, 18 were pulled from the sea while the rest remained in the sea," he said.

HTMS Sukhothai sank on Sunday evening about 37 kilometres off the coast of Prachuap Khiri Khan with 105 crew on board.

According to the navy, of the 105 crew members on board the ship when it went down, 82 had been found as of Wednesday, six were found dead, and 23 were still missing.