Thailand said on Saturday that there have been no new cases of the Middle East Respiratory Syndrome (Mers) since the first case was announced two days ago.
The patient - a 75-year-old businessman from Oman - is in a better condition now, the Public Health Ministry told reporters.
His three relatives are also in quarantine. Two of them, who had exhibited flu-like symptoms but tested negative for the Mers virus, are no longer feverish or coughing, said the ministry.
The number of people deemed to have been exposed to the virus has risen from 85 on Friday night to 175 on Saturday, according to the ministry.
The Omani man had turned up at the private Bumrungrad Hospital on Monday night accompanied by his relatives. He was tired and coughing, but not feverish, according to the hospital. He was later tested positive for the Mers virus.
The man and his relatives were moved to Bamrasnaradura Infectious Diseases Institute in Nonthaburi province just outside Bangkok.