A Thai naval vessel sank during a storm in the Gulf of Thailand on Sunday night. The ship had more than 100 sailors.
Authorities said 28 sailors were still trapped in the water after the HTMAS Sukhothai capsized on Monday.
No loss of life was reported in this incident. However, the condition of three crew members is critical.
Officials said the vessel sank after taking to water, flooding its hull and disrupting the power supply to its power room.
As the power system shut down, the crew struggled to maintain control of the ship.
The vessel was patrolling 32 km off the coast of Bang Saphan district in Prachuap Khirikhan province.
Three naval ships and helicopters were dispatched to assist, but only the frigate HTMS Crabtree arrived before the ship sank. The frigate rescued 78 of the 106 sailors aboard the Sukhothai, the navy said.
The navy said it was still rescuing another 28 soldiers, three of whom were in critical condition.
As of Monday morning, 28 people were in the water, the Navy said in a statement.
Authorities said searches continued through the night to locate all crew members.
Pictures published in local media showed the crew being carried away on stretchers by medics on the dock.