Thousands of dead fish, crabs and prawns were scattered down the picturesque Thung Wua Laen beach in the southern Thai province of Chumphon Thursday.

They were killed by toxic algae bloom known as the red tide, which depletes oxygen in the water and "prevents fish from breathing through their gills", local fishing authority Boonyawat Thonghom told AFP.

Local residents have been picking up dead fish along the two-kilometer stretch of white sandy beach.

"We advise the locals not to consume the fish as the algae might be toxic, but using them as fertilizer is OK," said Boonyawat.