A team of marine biologists and health experts is now investigating the death of the five-year-old boy at a beach on the famous island, best known for its rite-of-passage full moon revelries.
More than 10 Thai health officials and marine biologists are examining the circumstances of the case and trying to establish whether the boy's death means box jellyfish - the suspected cause of his death - are becoming more prevalent in the Gulf of Thailand.
Incidents involving box jellyfish are rare in Thailand.
Marine biologists will be researching the prevalence of jellyfish of all kinds in the Gulf and in the Andaman Sea on the other side of the Isthmus of Kra, the long peninsula that separates the two bodies of water.
Experts say that common vinegar is the only fluid that relieves the toxicity of a box jellyfish sting. Vinegar stations have been established as a precaution at most beaches in Thailand, especially on Phuket and along the Andaman coast.
The Director of Public Health for the province of Surat Thani, Dr Yongyos Tammawut, called in experts from Bangkok as soon as he heard about the incident at Phangan.
According to a spokesperson, the boy was stung badly on both legs while wading just a short distance from the beach at Khuad late on Saturday. There were no other people on the beach.
Staff at a nearby resort heard the boy's screams and rushed to douse his wounds with vinegar but his mother, perhaps in ignorance of the importance of vinegar, insisted they apply fresh water and ice instead, the spokesperson said.
The boy was being quickly transported towards the island hospital, about 10 kilometres from the beach, but died on the way.
Marine biologists will first try to confirm that the jellyfish involved was a box jellyfish, one of the world's most deadly creatures. ''Boxies'' have the ability to be carried long distances by currents.
Although sightings are occasionally reported in Thai waters, incidents seldom occur and deaths are extremely rare. Thai officials conduct surveys of jellyfish movements and precautions are taken to try to prevent fatalities.
Jellyfish are becoming more prevalent in all parts of the world.
The boy's parents are arranging for his body to be taken back to France for burial, the health spokesperson said.