Almost 200 new infections were reported on Sunday, and a "soft Lockdown" prompted thousands of people to leave Bangkok.
After the announcement of a Bangkok "soft lockdown", thousands of people flocked to bus stations to leave the city and the country.
Eighty thousand people boarded buses heading out of Bangkok on Sunday.
The number of Covid-19 cases rose to 599 with most of the new cases in Bangkok, said Public Health Ministry spokesman Thaveesilp Wisanuyothin. Dr Thaveesilp reported an increase of 188 new confirmed cases.
Shortly after Bangkok governor Aswin Kwanmuang ordered the closure for three weeks of shopping malls and markets except those selling food and essential consumer goods, five adjacent provinces of Samut Prakan, Samut Sakhon, Nakhon Pathom, Nonthaburi and Pathum Thani followed suit.
Responding to speculation of a full lockdown, Deputy Prime Minister Wissanu Krea-ngam said on Saturday the government had considered several measures to tackle the spread of the novel coronavirus.
He said whether these measures would be implemented depended on an evolving situation but noted that people "would be given a heads-up".
"Still, the government will have to consider people's safety as well as their convenience."
Following the closure orders by Bangkok and five other provinces, the national committee on communicable diseases stressed the need to screen passengers before boarding, to practise social distancing while away, and to clean and disinfect vehicles before and after the trips.
Transport officials have been instructed to obtain contact information from passengers too. Transport Minister Saksayam Chidchob said transport officials have been ordered to check the temperature of passengers.
Speaking at the daily news briefing on Sunday, Dr Thaveesilp said, of the rise in Covid-19 cases in Thailand, two groups were identified.
Of the first group of 65 cases, 21 were linked to the boxing stadium cluster in Bangkok, Loei, Nong Bua Lamphu, Udon Thani, Chon Buri, Phatthalung, Phra and Samut Prakan provinces; five related to entertainment venues; two associated with the religious activity in Malaysia, and 37 who were close contacts in Bangkok, Samut
Prakan, Sukhothai, Songkhla, Khon Kaen and Udon Thani.
The second group comprised 15 new cases; six Thai returnees and two foreign students from abroad, and seven working in crowded venues selling lotteries or goods at boxing stadiums.
The remaining cases were being investigated.
When asked if there would be additional measures to tackle the spread of the virus, Prime Minister Prayut Chan-o-cha said briefly: "We're working on it."
Source: Bangkok Post