The country registered 25,821 daily Covid-19 cases, 413 fewer than the prior 24 hours, the Public Health Ministry announced on Sunday morning.
The daily Covid death toll jumped by 17 to 84.
Just 56 of the new caseload were imported, with the remaining 25,765 transmitted inside the country.
The Centre for Covid-19 Situation Administration (CCSA) said in the afternoon that the 84 new fatalities were between the ages of six and 104, all of them Thai nationals.
Fatalities jumped from the 69 reported on Saturday, but were still a fraction of the number recorded during the height of the Delta wave in September and October last year.
(Screenshot from https://www.worldometers.info/coronavirus/country/thailand/#graph-cases-daily)
Bangkok logged the most new deaths at eight, followed by six in Samut Sakhon and five in Trat and Lop Buri.
The central region, including eastern provinces of Chon Buri, Rayong, Chanthaburi and Trat, recorded the most deaths at 23, six more than the southern region and eight higher than the Northeast.
The government has rolled out a nationwide vaccination drive for people aged 60 or more, with a plan to inoculate 70% of them by the end of this month to better protect them from possible infections during the Songkran holiday.
CCSA figures released on Sunday showed an uphill mission for health authorities to achieve the goal as only 4.4 million out of 12 million senior citizens - or 34.8% - had received a booster jab.
People aged 60 or more accounted for the most deaths in the country. The CCSA report on Sunday showed 87% of the fatalities fell into this group.
(Screenshot from https://www.worldometers.info/coronavirus/country/thailand/#graph-cases-daily)
Of the 25,821 new cases, Bangkok recorded the most - 2,749 - followed by 1,537 in Nakhon Si Thammarat, 1,293 in Chon Buri, 955 in Samut Sakhon and 870 in Samut Prakan.
The 56 imported infections were detected in travellers from 25 countries, led by six from Singapore and five each from Myanmar and Malaysia.
On Saturday, 251,936 people received Covid-19 treatment at hospitals, including 1,672 seriously ill patients and 644 dependent on ventilators.
During that 24-hour period, 24,066 Covid-19 patients were discharged from hospitals after recovering from the coronavirus.
(Screenshot from https://www.worldometers.info/coronavirus/country/thailand/#graph-cases-daily)
Since the pandemic started in early 2020, there have been 3,529,085 Covid-19 cases, including 1,305,650 cases this year.
The accumulated death toll stood at 24,799 since the beginning of the pandemic.
The highest number of Covid-related fatalities in a 24-hour period was 312 recorded on Aug 13. The highest number of cases was 27,071 on March 18.
Global Covid-19 cases rose by 1.2 million in 24 hours to 481 million. The worldwide death toll went up by 3,065 to 6.1 million. Thailand stayed at 14th in the international ranking.
