The government on Sunday recorded 237 new coronavirus cases, for an accumulated total of 23,371 since the pandemic began a year ago.
No new deaths were reported, leaving the toll at 79.
The Centre for Covid-19 Situation Administration (CCSA) said 112 of the new cases were found from active testing, 113 in hospitals and 12 from abroad.
Almost all the cases found through mass testing – 107 — were in Samut Sakhon, and all but three were foreign nationals. Active testing also revealed three new cases in Bangkok and two in Tak.
Samut Sakhon also dominated the caseload found at hospitals and clinics, recording 95 in the past 24 hours.
There were also 14 self-reported cases in Bangkok, three in Tak and one in Samut Songkhram.
The CCSA said a further 12 cases had arrived from overseas, including three Thai nationals entering the country through the Mae Sot checkpoint in Tak from the Myanmar town of Myawwaddy on Jan 28. The three were being treated at Mae Sot Hospital.
Nine other new cases entered Thailand through Suvarnabhumi airport: a Sri Lankan who flew in from Singapore; two Britons from the United Kingdom; one Thai returnee from Germany; one Japanese and one Thai from the Maldives; and one Italian, one Pakistani and one Irish national from France.
Deputy Foreign Ministry spokesman Natapanu Nopakun said the situation in Thailand was improving, with 14 provinces logging no new cases during the seven-day period starting on Jan 31.
The spokesman said health authorities in Samut Sakhon locked down two tambons, Nadee and Tha Sai, since more than 7,000 workers – mostly migrant labourers — in four major factories in the two areas had tested positive. The two tambons were under heavy restrictions.