The deadly sea creatures have been detected by a team of researchers working in cooperation between the Marine and Coastal Resources Research Centre and Chiang Mai University’s Faculty of Science.
Usawadee Dejsri, a researcher at the centre, said the surveys by the project, which have been carried out since late 2016, found that there are three types of Portuguese man-of-war in the bay referred to as the Norbakka, Chiropsoides and Chirnex.
She said her team had conducted 10 surveys of the deadly fish, finding last month that Portuguese man-of-war in the Trang Sea could kill a person in two or three seconds if more than 50 per cent of its body touched a person.
She said the body of Portuguese man-of-war grew larger in July when the seas were rough and several fishermen had been injured.