All workers returning from South Korea would be quarantined at assigned locations in military compounds, Prime Minister Prayut Chan-o-cha said on Wednesday.
More would be arriving from South Korea and they would not be allowed to return home right away, he said at Government House.
His stipulation follows a report from the Immigration Bureau that of 180 Thai workers who arrived back from South Korea through airports in the past three days, 19 were feverish and were quarantined for examination. They all later tested negative for coronavirus disease, Covid-19.
Their flights landed at Suvarnabhumi, Don Mueang and Phuket airports.
The other 161 workers were allowed to go to their homes right away, because they had no fever.
However, all the returnees were asked to stay at home for 14 days, the usual incubation period of the disease, the Immigration Bureau spokesman said.
Thousands of Thais who have been working illegally in South Korea are returning home to escape the spread of Covid-19 in South Korea, the biggest hotspot for the disease outside China.
The Seoul government earlier announced dispensation for illegal workers, known as phi noy, who leave, saying they will not be charged with overstaying or be blacklisted.