Health authorities confirmed on Thursday that the Covid-19 situation related to 10 illegal returnees from Myanmar's border town of Tachilek was under control.
Dr Kiatiphum Wongrajit, permanent secretary for health, said at the Public Health Ministry in Nonthaburi province that health officials had information about the whereabouts and timelines of the women, found people who had been in contact with them and kept them in safe places.
"A disease spread should be out of the question for now," he said.
According to Dr Kiatiphum, the 10 patients are in hospitals and have mild symptoms. Officials found 699 people had been in contact with them.
Among the at-risk people, 175 who had been in close contact with them tested negative and are in 14-day quarantine. The remaining 524 with a low risk of infection were also isolated.
The negative test results of high-risk people brought a relief and if they remain free of Covid-19 by the end of the quarantine, it could be concluded that the disease did not spread, Dr Kiatiphum said.
He also said that in general people who wore face masks had a low risk of infection. High-risk people are those without protective gear, talk to an infected person for more than five minutes, or stay at a crowded, narrow and poorly ventilated place for longer than 15 minutes.
People who were on the same flights as those taken by Covid-19 cases also have a low risk because air passengers are required to wear face masks, he said.
Dr Kiatiphum said that people should learn a lesson from the 10 returnees who dodged health-screening and quarantine procedures and caused economic damage.
An investigation found the women had sneaked back to a border village in Mae Sai district when local officials were changing shifts, he added.
Dr Opas Karnkawinpong, acting director-general of the Disease Control Department, said that officials in Chiang Rai province contacted their counterparts in Tachilek to seek information about Thai people stranded there.
He said 150 Thais in Tachilek had asked for permission to return to Thailand and they would go through an official border passage.