Three Omicron cases have been confirmed and a potential new one detected, according to the Department of Medical Sciences.
Dr Supakit Sirilak, director-general of the department, said on Thursday that the first confirmed case was an American man, 35, who arrived from Spain. The two others were Thai women who returned from Lagos, Nigeria.
He said whole genome sequencing confirmed the Omicron infection in the two Thai women aged 36 and 46.
On Monday afternoon health officials found a new potential Omicron case in a Thai man, 41, who worked for the United Nations and had just returned from the Democratic Republic of Congo, the director-general said.
The man had received two doses of the AstraZeneca vaccine and returned to the country through the Test & Go scheme.
An initial test found he was a potential Omicron case and officials were conducting whole genome sequencing with results expected in a few days, Dr Supakit said.
The new potential case was quarantined at a hospital and people who had come into close contact with him were being sought, he said.
"All the cases came from other countries. There has not been a locally transmitted case of Omicron," Dr Supakit said.
He also said that antigen test kits could be used to detect the Omicron infection, but they should be used repeatedly because initially the infections could be too weak for antigen tests to detect.
Omicron infections would spread worldwide but for the time being only four of about 1,600 people being monitored in the country might have the variant, Dr Supakit said. Omicron had yet to cause any deaths worldwide, so people should not panic.
"Basic infection prevention measures and vaccination can cope with it," he said.
The Centre for Covid-19 Situation Administration reported Omicron infections have been found in 59 countries: locally transmitted infections in 20 countries and imported cases in a further 39.
