Health officials are asking 290 people who came into contact with a Covid-19 patient in Krabi to closely monitor their health as 79 of them are considered "high-risk".
Although most of the man's relatives have tested negative, his wife's status is still unknown.
The man recently visited Krabi, Phuket, Chiang Mai and Sukhothai.
Doctor Walairat Chaifu said yesterday that the 37-year-old man, an Indian national who lives on Koh Phi Phi, had twice tested positive since Nov 4, when he had a health check while applying for a work permit.
He is now being kept in isolation at Krabi Hospital and health officials are waiting for test results to see if he has a highly spreadable version.
Although a Covid test he gave on Nov 6 was negative, that could be related to the fact that the positive test he'd given just two days earlier showed only small amount of the virus and because he had contracted the disease a long time previously. An immunity check also showed he had been infected for 1-2 weeks or longer, the doctor said.
"The infected person came to Thailand in April 2019, then went abroad in October before returning to Thailand in February and has not been anywhere abroad ever since. He opened a restaurant with his wife on Koh Phi Phi," Dr Walairat said.
Medical officers are trying to find those with whom he may have been in contact. From Oct 19-27, he was only on the island. On Oct 28, however, he went to Krabi by ferry and stayed with his brother's family.
On Nov 29, he travelled by car to Phuket and stayed in Patong and had a meal at a restaurant next to his hotel, Dr Walairat said.
On Oct 30, he went by taxi to Phuket Airport and flew to Chiang Mai, where he took another taxi to a bar. Both taxi drivers and the bar customers are considered at risk.
The next day, he went to Sukhothai, where he attended a Loy Kratong event, but other visitors are considered to be at lower risk of infection because everyone had their temperatures taken and face masks were compulsory.
