There were 4,886 new Covid-19 cases and 43 more fatalities registered during the previous 24 hours, the Public Health Ministry reported on Wednesday morning.
There were 4,721 cases in the general population and 165 among prison inmates.
The number of new cases rose from 4,306 announced on Tuesday, when the country recorded 37 more deaths.
On Tuesday, 6,326 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 2,091,895 Covid-19 patients, 1,998,328 of whom have recovered to date.
Since the pandemic started early last year, there have been 2,120,758 Covid-19 cases, with 2,025,754 complete recoveries so far.
The death toll stood at 20,720 during the third wave and 20,814 since the beginning of the pandemic.
Taweesilp Visanuyothin, spokesman for the Centre for Covid-19 Situation Administration, said in the afternoon briefing that the latest 43 fatalities were aged from five months to 100 years. The baby was born with heart disease.
Bangkok recorded two more deaths while another was reported in the adjacent province of Samut Prakan.
Other central plain provinces further from the capital reported 11 more deaths - in Lop Buri (2), Sa Kaeo (2), Chachoengsao (1), Chon Buri (1), Trat (1), Prachin Buri (1), Ratchaburi (1), Ayutthaya (1) and Rayong (1).
The South reported 15 more deaths – in Nakhon Si Thammarat (5), Songkhla (3), Krabi (2), Trang (1), Pattani (1), Phathalung (1), Yala (1) and Satun (1).
The North saw six new fatalities – in Phitsanulok (2), Chiang Rai (1), Phetchabun (1), Chai Nat (1) and Tak (1).
The Northeast had eight fatalities - in Nakhon Ratchasima (2), Kalasin (1), Khon Kaen (1), Chaiyaphum (1), Bung Kan (1), Amnat Charoen (1) and Udon Thani (1).
The 4,886 new cases included 4,175 local infections and six imported cases. Of the local infections, 4,566 were confirmed at hospitals and 149 via mass testing.
Bangkok had 794 new cases, followed by 270 in Songkhla, 240 in Surat Thani, 204 in Nakhon Si Thammarat, 198 in Chon Buri, 171 in Chiang Mai, 140 in Samut Prakan, 119 in Pattani, 117 in Prachuap Khiri Khan and 100 in Chumphon.
Dr Taweesilp said there were clusters of new Covid-19 infections at factories in Lop Buri, Prachin Buri, Saraburi, Phetchaburi and Kanchanaburi; markets in Khon Kaen, Udon Thani, Surat Thani, Prachuap Khiri Khan and Chanthaburi; workers’ camps in Rayong, Surin, Sa Kaeo and Khon Kaen; schools in Prachuap Khiri Khan, Sa Kaeo, Chiang Mai, Loei and Ubon Ratchathani; a military camp in Chon Buri; and eateries in Ubon Ratchathani and Udon Thani.
Since the country reopened to visitors on Nov 1, 133,061 people had arrived by air and 171 of them (0.13%) were confirmed with Covid-19, as of midnight.
“The infection rate of only 0.13% proves that the country's reopening was very worthwhile, and is bringing money to Thailand during the high season,” Dr Taweesilp said.
The six imported cases were from Ireland, Singapore, Japan, Cambodia, Switzerland and the Maldives.
On Tuesday 74,190 people received Covid-19 treatment at hospitals (down from 75,673), including 1,351 seriously ill patients (down from 1,353) and 340 dependent on ventilators (up from 329).
Global Covid-19 cases rose by 585,319 in 24 hours to 263.03 million. The worldwide death toll went up by 7,617 to 5.23 million.
Dr Taweesilp said the United States had the most new cases in 24 hours at 106,876, followed by 55,880 in Germany, 47,177 in France, 39,176 in the United Kingdom and 32,648 in Russia.
Most new cases were in Europe and the US while in Asia Vietnam recorded 13,972 new cases, ranking 11th worldwide by its number of new daily cases, he said.