There were a record 16,533 new Covid-19 cases, along with 133 fatalities, confirmed over the previous 24 hours, the Public Health Ministry reported on Wednesday morning.
There were 16,331 cases in the general population and 202 among prison inmates.
Since April 1, when the third wave of Covid-19 began, there have been 514,498 Covid-19 patients, 333,268 of whom have recovered.
Since the pandemic started early last year, there have been 543,361 Covid-19 cases, 360,694 of whom have recovered.
The death toll was at 4,303 in the third wave and 4,397 from the beginning of the pandemic early last year.
The previous high of daily infections was 15,376 reported on Monday.
The highest number of daily Covid-19 fatalities is 144, reported on July 17.
Bangkok led the country with 3,997 new infections, followed by Samut Sakhon (1,147), Samut Prakan (1,088) and Chon Buri (864), the Centre for Covid-19 Situation Administration (CCSA) said in its afternoon briefing.
The capital also reported the most fatalities, 45, followed by Samut Prakan (12), Nonthaburi (10), Nakhon Pathom (9) and Samut Sakhon (7). The rest were registered in 23 provinces.
The country also logged 10 imported infections, all Thai returnees, the CCSA said. There six who came from Myanmar, two from Malaysia and one each from the United Kingdom and the United Arab Emirates.