They were among at least 40 people who came into contact with the man. Those deemed to be at high risk included 22 passengers on his flight, two taxi drivers, four hotel staff, 11 hospital staff and one relative.
The man, 71, arrived in Thailand on January 22 with a fever that doctors in Oman could not treat, Thai officials said.
Last year, an Omani man also tested positive for MERS, leading to the quarantine of more than 170 people in Thailand. He was successfully treated and went home.
The MERS virus first appeared in 2012 in Saudi Arabia. It is considered a deadlier but less infectious cousin of Severe Acute Respiratory Syndrome (SARS), which killed hundreds of people when it first appeared in Asia in 2003.
It has so far appeared in 25 countries worldwide, including several Middle East countries, France, Germany, Italy, the Republic of Korea, Tunisia and the UK. No vaccine or treatment is currently available.
According to the World Health Organisation (WHO), about 36% of people known to have contracted MERS died as a result.