The country has seen its first confirmed case of the XAY.2 variant of Covid-19 but people close to the patient were not infected, according to the Department of Medical Sciences.
Dr Supakit Sirilak, director-general of the department, said on Friday that it had already shared information about the case with the Global Initiative on Sharing Avian Influenza Data (Gisaid).
XAY.2 is a hybrid of the AY.45 Delta variant and the BA.4/5 Omicron variant. So far there have been 344 cases of the hybrid reported worldwide, he said.
His deputy, Dr Ballang Uppapong, said the hybrid had an effect similar to the Omicron variant.
Dr Supakit also said that the country had not yet detected any instances of the highly transmissible Omicron XBB.1.5 variant, which is spreading fast in the United States.
The World Health Organization has said it does not have enough data yet on the severity of XBB.1.5, or a clinical picture on its impact. It said it saw no indication that its severity had changed but that increased transmissibility is always a concern.
Dr Supakit allayed concerns about incoming Chinese arrivals, saying that 97% of the new Covid-19 cases in China were of the older BA.5.2 and BF.7 Omicron variants, which do not spread any faster than Covid variants found in Thailand.
The dominant Omicron variant in Thailand is BN.1.3, which which is similarly transmissible and immune-invasive to XBB.1.5, he said.
Virologist Yong Poovorawan has also said that new Covid-19 strains from visitors arriving from western countries could pose a higher health threat that older strains from tourists arriving from China.
