A Hungarian diplomat based in Bangkok was found infected with Covid-19 after he shared a car and had dinner last week with the visiting Hungarian foreign and trade minister.
Tests on the minister's samples taken on his arrival later came back positive.
The Disease Control Department on Tuesday presented a timeline at a press conference of how the still unidentified 53-year-old Hungarian diplomat was infected.
On Nov 3, the diplomat had met Foreign and Trade Minister Peter Szijjarto when he and his delegation arrived by plane. They travelled in the same car to the alternative state quarantine facility at Anantara Siam Bangkok Hotel.
"On Nov 3, the diplomat was in the same car as the minister and they had dinner together with other delegates for 30 minutes that evening," department director-general Opas Karnkawinpong said.
Anantara Siam Bangkok Hotel on Wednesday disputed Dr Opas's version of events.
The hotel said in a statement that the minister had dined alone in his room after he arrived at the hotel, as required by health department quarantine regulations.
Dr Opas said that on Nov 4 the lab test showed the minister was infected. That same day, people who had been in contact with him were asked to go into quarantine, including the enbassy diplomat.
The minister and his delegation flew back to Budapest that day on chartered flights.
On Nov 5-8, the Bangkok-based diplomat took leave and self-isolated at home, Dr Opas said.
On Nov 9, the diplomat tested positive and was admitted for treatment at Bamrasnaradura Infectious Diseases Institute. He did not show any symptoms. Seventeen people who had been in close contact with him tested negative, Dr Opas said.
Dr Opas did not say the diplomat was infected by the minister. A separate press release issued by the Public Health Ministry on Tuesday was headlined that he was infected by the visiting minister.
Sophon Iamsirithavorn, the director of the Division of Communicable Diseases, said on Tuesday the diplomat had been in Thailand for about two years, so his case was treated as a local infection.
Others who were in contact with him were under observation and none of them had shown symptoms. All except the diplomat tested negative on their first test.
Meanwhile, the Centre for Covid-19 Situation Administration reported three new imported cases on Wednesday, bringing the tally of confirmed infections to 3,847.
A Thai woman's test on Monday was positive after she arrived from Turkey on Nov 4.
Another Thai woman who arrived from the United Kingdom the same day also tested positive on Monday
A British woman from the UK tested positive on arriving in Thailand on Sunday.
The death toll remains unchanged at 60.