The HTMS Sukhothai sank late Sunday roughly 37 kilometres (22 miles) off Thailand's southeastern coast, with a massive rescue operation managing to pull 76 crew alive from the waves.

Seventeen members of the 105-strong crew are still missing.

"Today we have recovered a total of six bodies," the navy said in a statement.

There is "preliminary evidence" that the bodies recovered Saturday were from the Sukhothai's crew, the statement said, adding they would be subject to DNA testing.

Six other bodies retrieved in the past week have been identified as Sukhothai crew members.

Helicopters, unmanned surveillance aircraft and warships have been combing the sea in hope of finding survivors.

The search also "received support from various local agencies", volunteers and the private sector, the navy said.

On Tuesday, Admiral Chonlathis Navanugraha called the incident "one of the most severe tragedies" in the navy's history.

The vessel -- a corvette, among the smallest of military warships -- ran into trouble after its electronics system was damaged.

The Sukhothai was commissioned in 1987 and built in the United States by the now-defunct Tacoma Boatbuilding Company, according to the US Naval Institute.