The government on Tuesday reported 427 new cases of the novel coronavirus, including 397 migrant workers, raising the accumulated total since the start of the pandemic to 5,716.
At least 16 of the new transmissions of the virus occurred in Thailand.
The virus was also detected in 14 people who recently arrived from other countries.
Dr Taweesilp Visanuyothin, spokesman of the Centre for Covid-19 Situation Administration, said the infected workers were detected during testing in the wake of the Samut Sakhon outbreak.
Sixteen locally infected people were linked to the shrimp wholesale market at the epicentre of the new outbreak in Samut Sakhon province.
They included five in Bangkok: a 49-year-old female vendor, a male worker, 28, a female government official, 54, and two other female vendors, aged 52.
Other locally infected cases were three vendors aged 21-45 in Saraburi, two vendors aged 37 and 42 in Pathum Thani, two vendors aged 36 and 37 from Samut Prakan, a female company employee, 24, in Chachoengsao, a female state enterprise worker, 57, in Nakhon Pathom, a 50-year-old female vendor from Phetchaburi and a female vendor, 48, from Uttaradit.
Dr Taweesilp said that about 1,000 seafood vendors from 22 provinces were frequent buyers at the shrimp wholesale market in Samut Sakhon and local health officials were alerted to test them and people in close contact.
The 22 provinces are Chiang Mai, Phetchabun, Nakhon Ratchasima, Suphan Buri, Kanchanaburi, Nakhon Pathom, Samut Songkhram, Ratchaburi, Phetchaburi, Prachuap Khiri Kan, Chumphon, Saraburi, Pathum Thanni, Ayutthaya, Nonthaburi, Bangkok, Songkhla, Samut Prakan, Prachin Buri, Chachoengsao, Chon Buri and Rayong.
Of the 397 infected migrant workers, about 90% were asymptomatic. They were among 2,015 tested people at the shrimp wholesale market in Samut Sakhon and 44% of all the tested people turned out positive, Dr Thaweesilp said.
The 14 newly confirmed cases among quarantined arrivals consisted of four from Pakistan, three from the United States, two from Sudan and one each from Bahrain, Switzerland, Germany, France and Kuwait.
Of the total 5,716 local cases, 4,078 (71.3%) had recovered, including 25 discharged over the past 24 hours, and 1,578 were being treated. The death toll was unchanged at 60.
Global Covid-19 cases rose by 534,219 in 24 hours to 77.71 million. The worldwide death toll was up by 8,899 to 1.71 million. The US had the most cases at 18.47 million, up 200,109.