Four medical personnel infected at quarantine facilities in Bangkok are among 19 new Covid-19 cases reported on Tuesday, raising the total to 4,126.
The 15 others are arrivals from eight countries.
The Centre for Covid-19 Situation Administration (CCSA) said seven cases were returnees from Myanmar, two from the United States and one each from Bahrain, Bulgaria, Denmark, Morocco, Turkey and the United Kingdom.
The four locally infected cases are nurses and colleagues aged 25-40 who worked at alternative state quarantine facilities and hospitals in Bangkok. They tested positive on Dec 4 and 5. People in close contact with them tested negative.
Three are women who had a fever, runny nose and headaches. The other is a man and was asymptomatic.
From Myanmar, six cases are Thai women, aged 24-37, who arrived on Dec 2 and 5 and were quarantined in Chiang Rai province.
They had worked at entertainment places and tested positive for Covid-19 either on day one or four after arrival. Their symptoms were aches, sore throats, runny noses and diarrhoea, loss of sense of smell and taste, and coughing.
The other case from Myanmar is a Thai housewife, 21, who sneaked back to Chiang Rai on Nov 29 and tested positive on Dec 5, but was asymptomatic.
The case from Bahrain is a Thai woman prison inmate, 32, who was confirmed as having Covid-19 on Nov 23. No other details were released.
The patient from Bulgaria is a Bulgarian businessman, 53.
The one from Denmark is a Danish male tourist, 73. The case from Morocco is a Thai woman, a student aged 24.
The case from Turkey is a Thai businesswoman, 38. The one from the UK is a Swiss male tourist, 65. The two cases from the US are a Thai man, 62, and a Thai woman, 61.
Of the 4,126 total cases in the country, 3,874 (93.89%) recovered including six discharged over the past 24 hours and 192 were at hospitals. The death toll remained unchanged at 60.
Global Covid-19 cases rose by 527,209 over the past 24 hours to 67.93 million. The worldwide death toll was up by 8,105 to 1.55 million.
The US had the most cases at 15.37 million, up 198,792, and the most deaths at 290,443, up 1,508.