Of the new cases, 781 were domestic infections and 21, imported, according to the Thai Centre for the COVID-19 Situation Administration (CCSA).
The centre said 692 out of the 781 local cases were found through active testing among Myanmar migrants and Thai nationals at factories and communities, mostly in Samut Sakhon.
Currently, Samut Sakhon remains the only province under maximum control plus restriction measures, while four others remain under maximum control, including Bangkok and three of its neighbours.
Thailand has so far confirmed 17,023 cases of infection, including 14,585 domestic and 2,438 imported cases.
Of that total, 11,396 patients have fully recovered and been discharged from hospitals while 5,551 others are currently hospitalised, with 76 fatalities.
Meanwhile, the Department of Health (DOH) of the Philippines reported 1,849 new COVID-19 cases on the day, bringing the total number of confirmed cases in the Southeast Asian country to 521,413.
The death toll climbed to 10,600 after 48 more patients died from the viral disease, the DOH said. It added 177 more patients recovered, raising the total number of recoveries to 475,765.
The Philippines, which has about 110 million in population, has tested over 7.2 million people since the COVID-19 outbreak emerged in January last year.