The Marine Department and Royal Thai Navy are trying to prevent oil leaking from a sunken tanker from reaching the coastline in Chumphon and Prachuap Khiri Khan provinces.
The department worked with the Tor 114 patrol boat and navy aircraft to contain an oil slick off Chomphon by deploying booms and using a solvent on Saturday night.
Deputy Transport Minister Athirat Rattanaseth said on Sunday that oil was drifting towards the coast in Pathiu district of Chumphon and three neighbouring districts of Prachuap Khiri Khan to the north: Bang Saphan Noi, Bang Saphan and Thap Sakae.
The Transport Ministry oversees the department.
The oil leaked from the Por Andaman 2, which sank on Saturday night while anchored about 24 nautical miles off Muang district of Chumphon. The tanker, belonging to Thai Laemthong Fishery Oil Trade Co based in Samut Prakan and with six crew on board, was carrying 500,000 litres of diesel oil when it sank to a depth of 50 metres.
Mr Athirat said all crew members were rescued by another ship, but the stricken tanker could not be salvaged due to strong winds and rough seas.
Navy spokesman Vice Adm Pokkrong Monthatphalin said the slick was about 10 kilometres long and moving in a northerly direction. He was concerned that more diesel might leak from the vessel.