There were 6,343 new Covid-19 cases and 45 more fatalities registered during the previous 24 hours, the Public Health Ministry reported on Monday morning.
There were 6,155 cases in the general population and 188 among prison inmates.
The number of new cases fell from 7,079 announced on Sunday, when officials also reported 47 more deaths.
On Sunday, 7,663 Covid-19 patients were discharged from hospitals after recovering from the coronavirus.
Since April 1, when the third wave of Covid-19 began, Thailand has treated 1,995,890 Covid-19 patients, 1,883,083 of whom have recovered to date.
Since the pandemic started early last year, there have been 2,024,753 Covid-19 cases, with 1,910,509 complete recoveries so far.
The death toll stood at 19,987 during the third wave and 20,081 since the beginning of the pandemic.
Taweesilp Visanuyothin, spokesman for the Centre for Covid-19 Situation Administration, said in the afternoon briefing that the 45 new fatalities were between the ages of 39 and 100 years and included two Myanmar nationals.
Bangkok recorded one new coronavirus-related deaths, with a further four reported in the adjacent provinces of Samut Prakan (2) and Samut Sakhon (2).
Other central plain provinces further from the capital recorded eight more deaths - in Chon Buri (2), Lop Buri (2), Petchaburi (1), Kanchanaburi (1), Prachin Buri (1) and Trat (1).
The Northeast had six fatalities - in Chaiyaphum (2), Nakhon Ratchasima (2) and Ubon Ratchathani (2).
The South reported 18 more deaths – in Songkhla (5), Phatthalung (2), Chumphon (2), Pattani (2), Phuket (1), Satun (1), Yala (1), Trang (1), Phangnga (1), Krabi (1) and Nakhon Si Thammarat (1).
The North saw eight new fatalities – in Chiang Mai (3), Nakhon Sawan (3), Uttaradit (1) and Uthai Thani (1).
The 6,343 new cases included 6,143 local infections and 12 imported cases. Of the local infections, 5,926 were confirmed at hospitals and 217 via mass testing.
Bangkok had 790 new cases, followed by 462 in Songkhla, 428 in Nakhon Si Thammarat, 376 in Chiang Mai, 318 in Pattani, 231 in Surat Thani, 207 in Yala, 193 in Narathiwat, 185 in Chon Buri and 168 in Samut Prakan.
Dr Thaweesilp said new cases were reported by prisons in many provinces, including 105 in Si Sa Ket, 29 in Nakhon Ratchasima and 20 in Kanchanaburi. Religious ceremonies led to 46 new cases in Phayao and 19 in Si Sa Ket over the past 24 hours.
The 12 imported cases were from Malaysia (1), Germany (1), Finland (1), the United Kingdom (1), Belgium (1), Myanmar (4) and Cambodia (3).
On Sunday 94,163 people received Covid-19 treatment at hospitals, including 1,776 seriously ill patients and 417 dependent on ventilators.
Global Covid-19 cases rose by 347,414 in 24 hours to 254.03 million. The worldwide death toll went up by 4,464 to 5.11 million.
The United States had the most cases at 47.92 million, up 24,193, and the most deaths at 783,565, up 126.
New cases were rising in western countries, especially those in Europe, where disease control measures were greatly relaxed including measures at stadiums, Dr Taweesilp said.
