The HTMS Sukhothai capsised late Sunday as it was patrolling the Gulf of Thailand, after water flooded its power controls. On Monday, authorities said they had rescued 75 sailors, but 31 were still missing in rough seas. 

Search crews worked through the night to find survivors, with the operation continuing on Monday with air force assistance. The operation involved two Seahawk helicopters, two frigates and one amphibious ship, the navy statement said. 

The navy also announced an investigation into the cause of the disaster.

"This has almost never happened in our force's history, especially to a ship that is still in active use," spokesman Admiral Pogkrong Monthardpalin told the BBC.

Footage shared by the navy on Twitter showed crew members wrapped in blankets and receiving treatment after they had been rescued. Some were being airlifted to hospital.

Other images showed sailors from the Sukhothai in a life raft, having jumped from the sinking vessel.

One unnamed crew member said he had been in the water for several hours before he was rescued. 

"The waves were quite high, about three metres when the ship sank," he said in a clip shared on local media. "I put on the life jacket and jumped. I swam for three hours."

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," a spokesperson said.

BBC