Pickup trucks were submerged by flash floods amid storms and heavy rain in southern Thailand, where a navy ship sunk leaving 30 crew missing.

Roads were swamped by the deluge forcing drivers to flee their vehicles in Hat Yai, Songkhla province, on Sunday morning December 18.

The Meteorological Department warned of 'four metre high waves' battering regions along the eastern-facing coastline. Officials said the heavy rain would continue until December 20 in Surat Thani, Nakhon Si Thammarat, Phatthalung, Songkhla, Pattani, Yala and Narathiwat along the border with Malaysia.

Storms at sea over the weekend have caused chaos for vessel. A navy warship sank in the Gulf of Thailand off the coast of Prachuap Khiri Khan province leaving 30 people missing at sea on Sunday.

An oil tank also ran aground in Songkhla while nine seamen were rescued in Surat Thani province when a cargo ship sank during storms.

Government agencies across the region have been warned to brace for severe flooding.