Thai navy searches for 31 sailors after vessel sinks

Thai military frigates and helicopters were searching for 31 sailors after a naval vessel sank, with dozens of others having been hauled from choppy waters.

The HTMS Sukhothai capsized as it was patrolling the Gulf of Thailand, about 37 kilometres 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.

However, 31 sailors were still missing, 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.

A statement from the Royal Thai Air Force said they were also assisting in the operation, without giving details.

Prime Minister Prayut Chan-o-Cha said the cause of the incident was being investigated.

"I am following the news closely, about five people are seriously injured," he added in a statement.

The navy later said the search was still ongoing over an area measuring around 20 miles by 15 miles, concentrating on a section of sea roughly 18 miles south of the Sukhothai's last position.

The vessel is believed to have run into trouble after its electronics system was damaged, according to the navy.

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