Four Thais returning from New Zealand were found to have a high fever on their arrival at Suvarnabhumi airport on Wednesday night.
Health and airport authorities said the four returnees were taken to a hospital after health screening at the airport detected high body temperatures.
The four returned to Bangkok on Thai Airways International flight TG492 from Auckland, which carried 179 passengers, two of them New Zealand businessmen. The others were taken to Bangkok Palace Hotel for state quarantine.
Sixteen passengers also arrived at the airport from Kathmandu on Nepal Airlines flight RA4011 and were taken to Arnoma Grand and H2Do hotels. Another 11 on Air India flight AI1302 from New Delhi were taken to the Arnoma Grand for 14-day quarantine.
All passengers from Nepal and India passed health screening at Suvarnabhumi.