Two more dugongs were found dead on Sunday, one off the coast of Krabi and the other in Trang, bringing the death toll to five in four months, said Kongkiat Kittiwatanawong, director of Phuket Marine Biological Centre.

In Krabi, the dead dugong was pulled out of the sea between Koh Pu and Koh Phi Phi. The other dead dugong was found washed ashore on Hat Samran beach in Trang's Hat Samran district.

The Krabi dugong was a 2.3-metre long male weighing about 400kg, said Woraphot Lomlin, head of Hat Noppharat Thara National Park-Phi Phi Archipelago in Krabi.

It was transported to Rajamangala University of Technology Srivijaya's Trang campus for an autopsy, he said.

The Krabi dugong was the fourth death, and the Trang dugong the fifth, in the past four months, said Mr Kongkiat in his Facebook post on Sunday.

Thon Thamrongnawasawat, deputy dean of Faculty of Fisheries of Kasetsart University, said the dugongs may have been hunted for their tusks which are made into talismans.

The expert said the earlier rescues of two young dugongs, named Mariam and Yamil, had captivated the public.

Those two young dugongs are now being nursed under the care of the Department of Marine and Coastal Resources.