Prime Minister Prayut Chan-o-cha has told the Public Health Ministry to prepare for a new Covid-19 lockdown in case the pandemic spirals out of control.

Prayut said on Monday that public health officials were testing migrant workers as far and wide as possible.

He said everyone should cooperate with the government and health authorities in containing the spread of Covid-19 among migrant workers "or else a lockdown will become unavoidable".

The prime minister said he wanted to spend seven days to assess the Covid-19 situation to decide whether the New Year countdown should be held or not, as well as Children's Day.

He asked the public not to panic and hoped the situation would improve after seven days.

The Centre for Covid-19 Situation Administration (CCSA) said it was still impossible to decide whether New Year celebrations should be cancelled.

The CCSA recorded 382 new infections on Monday, 360 of whom were migrant workers, as health authorities sped up screening migrant workers in Samut Sakhon potentially linked with the province's central shrimp market, a new virus hotspot.

Apartments where migrant workers live are being turned into makeshift quarantine centres. This approach should contain the spread of the virus.