The infected employee, a male engineer, tested positive after attending a training session in the office of Map Ta Phut Olefins Co Ltd (MOC) in Rayong province on February 28.
The man had joined the meeting with 40 employees of the company but as of now, other employees have not shown symptoms of Covid-19, the company said.
The MOC will follow the measures outlined by the Department of Disease Control by sanitising the training session room and allowing the other employees to take leave for 14 days to be on quarantine.