The Omicron variant has been detected in two foreigners visiting Chiang Mai who tested positive for Covid-19.

The tourists were a German and a British national who arrived in the country under the quarantine-free programme, Test & Go, through Suvarnabhumi airport.

Chiang Mai's governor said the German visitor, 22, passed an RT-PCR test after arriving in Bangkok on Dec 17 and travelled to the northern province on a Thai Lion Air flight on Dec 20.

He stayed overnight at a condo in Chang Klan and travelled to Mae Wang for a jungle trip on Dec 21. He felt exhausted upon his return, and a Covid-19 test at a hospital the following day was positive.

His sample was sent to a lab at the Medical Sciences Centre in the province and the result "potentially matched the B.1.1.529 Omicron strain".

The governor said 18 people were at high-risk due to close contact with him, including 13 passengers who sat near his seat on the plane.

Four passengers on the same flight and a taxi driver tested negative, and health authorities were waiting for the test results of the eight others, he added.

The other case was a 64-year-old British tourist who arrived in Bangkok on Dec 18 and passed an RT-PCR test.

He came to Chiang Mai the next day on a THAI Smile flight and stayed at a house in San Sai district. On Dec 24, he took an antigen test and the result came out positive.

He then visited Doi Saket Hospital for an RT-PCR test and was admitted there when the positive result was confirmed.

The governor said testing on two friends came out negative and authorities were awaiting test results on another friend. They were searching for a number of passengers who sat near him on the plane and one taxi driver.