The mass gatherings, or blooms, of box jellyfish in coastal areas around Thailand each year attract large groups of tourists, but they can also be very dangerous for swimmers.
Last Saturday, a five-year-old boy died after being stung by a box jellyfish on a popular beach on Ko Phangan, a resort island in Surat Thani.
Yongyos Thammawut of the provincial public health office in Surat Thani said the boy went into shock from stings from the poisonous tentacles of a box jellyfish while with his parents on Khuad beach Saturday. He died as his parents and a guide were taking him to Phangan hospital for treatment, Dr Yongyos added.
The boy became entangled in the box jellyfish's 20 cm-long tentacles.
As a result, Phangan acting district chief Kasitdet Thongchu on Monday asked local administrative authorities and beachside hotels to post signs warning of poisonous jellyfish and to prepare first aid in case swimmers are stung by them.
Fully grown box jellyfish, some of the most-poisonous animals on earth, can reach three meters long.