The outbreak began at a shrimp market in Samut Sakhon, a province in southwest Bangkok and a center of the marine industry that hosts thousands of migrant workers.
“Today is just the first stage,” Kiattiphum Wongrajit, the ministry’s permanent secretary, told a news conference. “Subsequent results will show many more infections.”
He said up to 40,000 people will be tested in Samut Sakhon and nearby provinces, with more than 10,000 tests to be conducted on Wednesday.
Migrant workers, mostly from Myanmar, lined up for tests on Sunday, along with some Thais. Most of the cases identified so far have been asymptomatic, health officials said.
The barbed wire surrounded the market on Sunday as Bangkok authorities ordered the closure of all schools in the capital’s three districts bordering Samut Sakhon, 45 kilometers (30 miles) by road, until 4 p.m. gener.
The province will remain under closure and night curfew until Jan. 3, and Kiattiphum said the ministry hopes to control the situation in two to four weeks.
“We need to reduce the epidemic cycle”
Prime Minister Prayuth Chan-ocha posted on his Facebook account: “We will have to quickly reduce the cycle of the epidemic. We already have experience in handling it.”
Bangkok authorities also called on people to intensify preventive measures by avoiding meetings, while entertainment venues and restaurants must observe social distancing.
Organizers of New Year’s celebrations were told to ask for official permission to move on, while companies were urged to get staff to work from home, if possible.
Meanwhile, Cambodia’s neighbors tightened requirements for people entering the country from Thailand.
Somsak Paneetatyasai, president of the Thai Shrimp Association, said the outbreak was bad news for shrimp exports, up to 30% of which come from Samut Sakhon. Thailand is one of the top ten shrimp exporters in the world.
The rise in coronavirus cases comes as Thailand attempts to revive a pandemic-ravaged tourism industry. On Thursday, Thailand eased restrictions to allow the return of more foreign tourists.
Additional reports from CNN’s Kocha Olarn and Nectar Gan.