The eruption began at a shrimp market in Samud Sakon, a province southwest of Bangkok, and is the center of a seafood industry inhabited by thousands of migrant workers.
“Today is the first phase,” the ministry’s permanent secretary, Giottipam Vonkrajit, told a news conference. “Further results will show a lot of infections.”
He said up to 40,000 people will be tested in Samud Sakon and nearby provinces and more than 10,000 will be tested by Wednesday.
Most of the migrant workers, mostly from Myanmar, lined up for the test on Sunday with some Thais. Health officials said most of the cases identified so far were asymptomatic.
The barbed wire market was cordoned off after authorities in Bangkok ordered all schools in three districts in the capital, which borders 45 kilometers (30 miles) away, to close until January 4.
The province remains under lock-up and night curfew until January 3, and the ministry expects the situation to be brought under control in two to four weeks, Giatpam said.
‘We need to reduce the epidemic cycle’
Prime Minister Prayut Chan-ocha posted on his Facebook account: “We need to reduce the epidemic quickly and we already have the experience to deal with it.”
Authorities in Bangkok called on people to step up preventive measures by avoiding meetings, while entertainment venues and restaurants should pay attention to social distance.
Organizers of the New Year celebrations were told to get official permission to go ahead, while companies were urged to get employees to work from home if possible.
Neighboring Cambodia, meanwhile, is in dire need of people entering the country from Thailand.
Somsak Panidadayasai, president of the Thai Shrimp Association, said the deaths were bad news for shrimp exports, with up to 30% coming from Samud Sakon. Thailand is one of the 10 largest shrimp exporters in the world.
Cases of the corona virus are on the rise as Thailand seeks to revive a tourism sector devastated by the epidemic. On Thursday, Thailand eased restrictions on allowing more foreign tourists to return.
Additional report by CNN’s Kocha O’Lourn and Nectar Khan.