The government on Wednesday banned all gatherings "posing a risk of disease transmission", effective immediately in Covid-affected zones.
The latest clampdown was announced after the country recorded 250 new cases in a single day.
The ban applies to any gatherings that pose a risk of spreading the coronavirus, exploit opportunities to compound people's hardship or intend to spread the disease.
With the country now designated into zones according to the severity of each area's situation, those gatherings and activities that would draw crowds in "maximum control zones" and "control zones" are prohibited.
However, two exceptions were also announced: government activities and gatherings held in private households.
Gatherings and activities in government-designated "close surveillance zones" and "surveillance zones" can take place if they receive prior approval from provincial governors.
Again, these do not apply provincially for household gatherings and government activities.
Provincial governors will announce which areas are designated maximum control, control, close surveillance and surveillance zones.
They will also set their own quarantine policies for new arrivals, said Dr Taweesilp Visanuyothin, spokesman for the Centre for Covid-19 Situation Administration (CCSA).
Violators will face punishment under Section 18 of the Executive Decree on Public Administration in Emergency Situations.
The section carries a jail term of up to two years and/or a fine of up to 40,000 baht.
The new ban was issued by the chief of defence forces, Gen Chalermpol Srisawasdi, in his capacity as the official handling security-related emergency situations.
The announcement came after the latest Covid-19 outbreak was found to have spread to a majority of Thailand's provinces.
Two hundred and fifty new cases were recorded on Wednesday, including 241 transmitted locally, eight returnees in state quarantine and one who sneaked into the country illegally, Dr Taweesilp said.
He added the CCSA had divided the recent outbreak into three distinct clusters. The first is linked to the Central Shrimp Market in Samut Sakhon, the second to illegal gambling dens in Rayong and the third to entertainment venues in Bangkok. A further group of infections is also being investigated.
Infections related to the shrimp market are likely to decline with just 28 new cases reported on Wednesday, raising the total to 1,634.
The infections linked to illegal gambling dens in Rayong have been reported outside the province, with Chon Buri on Wednesday reporting 108 new Covid-19 cases linked to this cluster. Meanwhile, infections linked to entertainment venues in Bangkok rose to 125.
Opas Karnkawinpong, chief of the Department of Disease Control, said the situation in Samut Sakhon, Bangkok and its neighbouring provinces, plus Rayong and its neighbouring provinces was being closely watched following a tightening of disease control measures.
The Chon Buri governor on Wednesday reacted to news of a spike in infections by declaring Pattaya and the rest of Bang Lamung district as a maximum control zone. This means that schools, childcare centres, entertainment venues and cinemas are among businesses that are to shut immediately. Dining out is banned and convenience stores must close from 10pm-5am. However, travel in and out of Bang Lamung is still allowed.
The governor also declared Muang district as a control zone and the remaining districts as surveillance zones.
Rayong, where five districts are declared as maximum control zone, on Wednesday reported 54 new cases, bringing its total to 202. Field hospitals are being arranged and are expected to be ready in three days.
In Bangkok, 17 new cases were reported on Wednesday and were traced to three risk areas: the shrimp market in Samut Sakhon, the city's entertainment venues and a shoe-making factory in Bang Khun Thian district.
The entire province of Nonthaburi was declared a control zone, with Talad Klang Bang Yai -- Bang Yai's central market -- designated a maximum control zone after being linked with all 21 new cases reported on Wednesday. Vendors are being strongly advised to take Covid-19 tests but those with a clean bill of health will be allowed to carry on working.
A condominium in Bang Yai district will be sealed off until Jan 12 after Covid-19 cases were reported there. The building reportedly houses more than 100 migrant workers from Myanmar. The Public Health Ministry has ordered all provincial communicable disease control committees to draw up a Covid-19 response plan tailored to the situation in their provinces.
It has also ordered the committees to make sure that activities to celebrate the New Year are not allowed in maximum control zone and that migrant workers avoid gathering, socialising or travelling to other provinces.
