SONGKHLA: Blue bottle jellyfish have invaded Samila and Chalathat beaches on the southern coast of the Gulf of Thailand, with many swimmers having been stung.
Local residents warn visitors that the jellyfish can inflict a nasty, burning rash.
It resembles a small, floating blue balloon and children should be warned not to play with it. Its sting could also be dangerous for the elderly, asthmatics and people with allergies.
Pornthip Lohitchat, 55, a somtam vendor at Samila beach, said many people who went into the sea off the beach recently had been stung.
Before, there were signs at the beach warning swimmers to beware of jellyfish. However, the signs were no longer there. They had possibly been washed away by waves, she said.
The sting is inflicted by long tentacles that trail in the water below the buoyant blue-green body. The tentacles are there to catch small fish. The jellyfish are moved by prevailing winds and currents.