The government reported 1,335 new coronavirus cases on Wednesday, the highest number of daily infections since the epidemic emerged in Thailand early last year.
The Centre for Covid-19 Situation Administration said that of the 1,335 new infections, only nine were among arrivals from overseas. This brings the total number of confirmed cases to 35,910. The death toll remains unchanged at 97.
Wednesday's figures were the highest since Covid-19 disease was first reported in Thailand.
Bangkok had the most new cases at 351, followed by Chiang Mai (319) and Prachuap Khiri Khan (161).
Opas Karnkawinpong, director-general of the Department of Disease Control, said most cases were linked to nightspots.
Prime Minister Prayut Chan-o-cha has ordered officials in all state agencies to work at home until the end of the month if possible and recommended that the private sector follow suit, to help to contain the spread of the third outbreak.
Dr Opas said limiting the movement of people would curb the pandemic. Every province could play a key role.
"Every provincial communicable disease committee is a frontline in helping minimise the movement of people," he said.
Authorities in 43 provinces have imposed restrictions on visitors to discourage travel. Surin was the latest, joining 42 others on Tuesday night, according to the Interior Ministry.
The CCSA said the imported cases were three from Malaysia, two from the United States and one each from India, Bangladesh, Nepal and Russia.
