The cases, both Thais and foreigners, were found at quarantine centres in Bangkok, Samut Prakan and Chonburi provinces.
A Thai woman in Samut Sakhon province tested positive. Health authorities are checking the source of her infection as well as her close contacts.
The 15 imported case include:
▪︎Four Thai women, aged 25, 25, 36, 41, who had travelled back from Myanmar.
▪︎A Thai boy, 9, two girls, 5 and 10, two female teachers, 28 and 39, who had returned from Saudi Arabia.
▪︎ A Thai female trainer, 24, from the United Kingdom
▪︎An Indian male student, 22, a Dutch man, 63, a Swiss girl, 2, and a Swiss man, 61, from their respective countries.
▪︎ A Belarussian woman, 27, from Turkey.
A female prawn merchant in Samut Sakhon, 67, tested positive for Covid-19 at Mahachai Hospital before she was transferred to Samut Sakhon Hospital. Initially, 26 people were considered high-risk close contacts, including her family members, a housemaid, medical officers and two Burmese employees; 13 have tested negative, 10 results are awaited and three people -- her mother, elder sister and daughter-in-law -- have tested positive. The three who have tested positive will be tested again and their situation confirmed on Saturday, Dr Sophon Iamsirithaworn, general communicable diseases director at the Department of Disease Control, said.
Some 139 people are considered as low-risk close contacts, which includes workers in a fish market, bringing the number of those in close contact to 165 people.
From December 1-13, the patient had sold prawns at the fish market from 6am to 11am every day. Her eldest son, 39, was immediately quarantined.
She suffered mild symptoms with muscle ache and loss of sense of smell on December 13. Three days later, she went to Mahachai Hospital, met eight health officers and took a Covid test at 6pm, then returned home. The hospital confirmed a positive result at 10pm and asked her to return to the hospital for quarantine.
The patient later was sent to Samut Sakhon Hospital on December 17 at 2.30am and tested again. The test result was again positive in the morning at 8am.
A Samut Sakhon provincial official confirmed that her residence area and the fish market have been disinfected.
Meanwhile, 16 patients have recovered and been discharged.
The total number of confirmed cases in Thailand increased to 4,297 (1,302 in state quarantine), 232 are in hospital, 4,005 have recovered and been discharged and 60 have died.
According to Worldometer, as of 10am on Friday, the total number of confirmed cases increased to 75.27 million (up by 721,392), 52.84 million have recovered, 20.76 million are active cases (107,213 in severe condition) and 1.67 million have died (up by 12,825).
Thailand ranks 152nd for most cases in the world, while the US has the most number with 17.62 million, followed by India 9.97 million, Brazil 7.11 million, Russia 2.76 million and France 2.42 million.