The badly decomposed remains of an unidentified 10-metre long Baleen Whale (Mysticeti) were washed up on the coast of Khong Yai District in Trat Province.

Source: Department of Marine and Coastal Resources (DMCR) of Thailand Facebook

A possible candidate would be the Bryde’s Whale, which is known to inhabit the Gulf of Thailand. The taxonomy of the Bryde’s Whale is still far from settled; what we call the Bryde’s Whale has been split into two subspecies or even distinct species by some authorities: the true Bryde’s Whale, a larger species found in tropical and warm temperate waters worldwide (Balaenoptera brydei), and the Eden’s Whale, a smaller form that may be restricted to coastal waters of the Indo-Pacific (Balaenoptera edeni). Both species(?) have been recorded from tropical waters of Southeast Asia.

The fish raised by farmers in Trat have died due to an unknown cause. (Photos by Jakkrit Waewkraihong)

Thailand: Trat village probes mass fish kill
By Jakkrit Waewkraihong, 4th August 2015;

Officials in Trat province are trying to determine what caused a mass fish die-off in a Muang district canal.

Fish, crab, shrimp and other marine life died in the Khlong Son canal over the past 24 hours. Boonnote Phumanee, head of Saphan Hin village, went to the waterway Tuesday morning after residents reported the strong stench of fish as far as a half-kilometre away.

In the upper section of the canal, which flows into the sea, some Asian sea bass (Lates calcarifer) and Grouper (SubF. Epinephelinae) raised in baskets also died.

Fish raisers said they suspected water in the canal, which had turned reddish brown, caused the fish to die. Residue of a yellow liquid were found covering the beach for about 200 metres and in the sea. It was not yet known where the liquid came from.

The village headman said water samples would be taken for testing.

Some villagers alleged the reddish-brown water was from a shrimp farm owned by a high-level police officer, but that had not been confirmed, Mr Boonnote said.

Source: Bangkok Post

Based on the photo, at least one Spotted Scat (Scatophagus argus) was the victim of this mass mortaity event.