The Centre for Covid-19 Situation Administration (CCSA) on Sunday admitted the current Covid outbreak is more serious than the first wave early this year.

Taweesilp Visanuyothin, spokesman for the CCSA, said the number of infections jumped by over a thousand over a short period of time, suggesting the spread of the virus this time is far more serious than the first wave, which began at the start of the year.

A total of 121 new Covid-19 cases were reported on Sunday, 94 of which were local transmissions.

The number of accumulated cases rose to 6,141 on Sunday, compared with 4,331 before the outbreak in Samut Sakhon began in mid-December.

Covid-19 cases linked to the Central Shrimp Market in Samut Sakhon have now been found in 38 other provinces, the CCSA spokesman said, as Sukhothai, Lop Buri and Surin reported their first linked cases on Sunday.

"Whether or not the disease control measures will be intensified will depend on how much the public cooperates. If we cooperate, there will be no need to enforce the law, impose lockdowns or a curfew," he said.

Dr Taweesilp said everyone should continue wearing face masks in public and avoid large gatherings, saying they can still hold small parties with close friends and family members.

He also said gamblers in Rayong were withholding information about their activities, which could hamper health officials' efforts to contain the virus.

A new cluster of Covid-19 infections was found in Rayong, which is linked to an underground casino in Muang district.

The area has been declared a maximum control zone -- where the tightest Covid-19 control measures apply -- after 27 new infections were confirmed in a single day on Saturday.

The number has increased to 85 as of Sunday.

Meanwhile, Prime Minister Prayut Chan-o-cha is urging the public to use the "Mor Chana" application to track Covid-19 cases around them.

The application, launched in April, can help warn individuals who have been exposed to infected patients by using GPS and Bluetooth technology to track their location.