Prime Minister Prayut Chan-o-cha has urged the public not to panic following the first confirmed case of the deadly Mers virus in the country.
"The prime minister would like the public not to get in a panic. People should follow all advice given by public health authorities," government spokesman Sansern Kaewkumnerd said.
Maj-Gen Sansern said the Public Heath Ministry was following all the procedures in line with international standards to control the deadly virus.
The 75-year-old patient came to Thailand from Oman, Maj Gen Sansern said.
He is being treated at Bamrasbaradura Infectious Diseases Institute in Nonthaburi province.
The Public Health Ministry said the man came to Thailand on June 15 for heart treatment at a private hospital and the hospital had separated him from other patients before referring him to the institute.
His condition was stable, the ministry added.
Health officials are monitoring 59 people who were in contact with him during his visit to Thailand. Some are being quarantined at hospitals while the rest are allowed to stay at home with health conditions to be checked every day, it said.