A cargo vessel carrying 290 shipping containers sank near Kaeo Noi Island, off the coast of Phuket, on Saturday afternoon.
Fourteen of the containers are reported to contain hazardous substances.
According to the Phuket Marine Department, the 4,339-tonne container ship was en route from Malaysia to Bangladesh when it foundered.
The cause of the sinking has not yet been determined.
The vessel listed heavily, causing many containers to fall into the sea. Some sank immediately, while others remain afloat and have drifted over a wide area, posing a hazard to navigation.
The Royal Thai Navy has dispatched HTMS Hua Hin, HTMS Panyee and two patrol boats to the scene to monitor the situation.
Naval divers are installing cardinal and isolated danger markers on and around the floating debris to warn other mariners, the Marine Department said, adding that relevant officials and equipment are on standby to respond to any oil spill or release of hazardous materials from the wreck.
