The HTMS Sukhothai capsized late on Sunday night as it was patrolling the Gulf of Thailand, about 37 kilometers (22 miles) off the nation's southeastern coast.

Some sailors survived by jumping into a life raft at night, according to images shared by the Royal Thai Navy, which said 75 people had been rescued, AFP reported.

However 31 sailors were still missing on Monday afternoon, according to navy spokesperson Admiral Pogkrong Montradpalin.

The search and rescue operation involved two seahawk helicopters, two frigates and one amphibious ship, according to a navy statement.

The spokesman said the vessel had sunk after its electronic system had been damaged.

"The ship's operating systems stopped working, causing the ship to lose control," he said.

Another image shared by the navy showed the vessel as it was capsized, while a video showed a rescue boat alongside it in choppy waters.

Other images shared by the navy's Twitter account showed men wrapped in blankets following the rescue.

Several areas in southern Thailand have been hit by storms and flooding in recent days.

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

A tourist boat carrying mostly Chinese visitors capsized in 2018 off Phuket island on Thailand's west coast.

More than 40 people died in the accident, one of the worst boat disasters in the recent history of Thailand.