At least three people have died after a freak storm sank 10 fishing boats off southern Thailand on Sunday.

Hundreds of crewmen aboard around 60 vessels that set sail off the coast of Nakhon Si Thammarat province were caught by surprise when the inclement weather struck without warning on Sunday morning April 16.

Local media reported that at least three people were found drowned while seven more were still missing as of Monday.

Search and rescue operations are continuing today off the coast of the region's Pak Phanang district.

Three marine police boats and one helicopter from Air Wing 7 in Surat Thani province have been deployed, Nakhon Si Thammarat Governor Apinan Puakpong said.

Thailand and neighbouring countries in Southeast Asia are approaching their annual monsoon rainy season which sees soaring temperatures followed by powerful rain storms in the afternoon leading to widespread flash floods.