About 80 Thai returnees from South Korea who "slipped through" a new screening process at Suvarnabhumi airport on Saturday are being told to report to health authorities in three days or face legal action under the Communicable Disease Control Act.

Deputy Public Health Minister Sathit Pitutecha, who is in charge of handling Thai workers who returned from working illegally in South Korea under an amnesty programme, said health authorities have the identities and contact details of this group of passengers, which can be used to track them down.

"But we're advising them to report to provincial health authorities within three days. If they don't cooperate, we have no choice but to strictly enforce the laws. If arrested, they face a one-year jail term and a fine of 200,000 baht," he said.

Illegal workers known as phi noi ("little ghosts") with travel history to Daegu and North Gyeongsang will be quarantined at a navy facility in Chon Buri's Sattahip district.

Returning illegal workers who are deemed less of a risk will be sent to regional screening venues to determine if they should be placed in state-designated quarantine venues, or sent home for self-quarantine.

Other passengers will be advised to perform a 14-day self-quarantine and required to report their condition to health officials every day.

The government's readiness to cope with the influx of illegal Thai workers from Covid-19 hit-South Korea has been criticised after posts and reports on social media claim several returnees ignored requests to self-quarantine for 14 days.

As of Sunday evening, a total of 143 illegal Thai workers from South Korea had been sent to the navy facility in Sattahip for quarantine.

The first batch of 60 arrived there late on Saturday night; 59 boarded the buses and another woman took a taxi from the airport to join the group later.

The Royal Thai Navy has prepared six buildings at the reception centre to accommodate those from Daegu and North Gyeongsang. The facility can hold up to 780 returnees.

The facility, guarded around the clock by naval personnel, was used to quarantine 138 Thais who returned from China's Wuhan last month.