BANGKOK (BLOOMBERG) - Thailand is bracing itself for the emergence of new Covid-19 clusters as the highly infectious Delta variant rips through more regions outside of its current epicentre of Bangkok metropolitan region.

About 60 per cent of Thailand's new coronavirus cases in recent days have been reported from outside the capital region, with low vaccination rates and looser movement curbs, official data showed.

The country's rate of new infections per million population at nearly 300 now dwarfs that of Indonesia or India, with a new daily record of 21,379 cases reported on Friday (Aug 6).

The rapid spread of Delta may force the government to extend and expand the crippling Covid-19 containment measures that already cover 40 per cent of Thailand's population and three-quarters of the economy.

The worsening outbreak may also scuttle plans to reopen borders to fully vaccinated tourists from mid-October and jump-start the tourism reliant economy that has seen the country's currency tumble to a three-year low.

Over the past several weeks, Delta variant cases have surged in nearly all provinces in Thailand, with nearly 80 per cent of new infections nationwide now caused by the strain first detected in India.

While Covid-19 restrictions may not result in a rapid decline in infections, they will help slow the spread and reduce pressure on the health system as the pandemic is likely to ease only from next month or October, the Thai health officials have said.

The authorities mounted an aggressive vaccination drive in the capital region to quell the outbreak along with lockdown-like restrictions. While nearly 70 per cent of residents in Bangkok have received their first shot, only about 21 per cent of the population nationwide have got their first jabs, Health Ministry data showed.

By focusing on only the virus hot spots, the government risks creating more clusters in regions currently not under a lot of restrictions, according to Dr William Aldis, a former country representative for the World Health Organisation in Thailand.

"The failure to get anywhere near the vaccination rate Thailand should have at this point is a catastrophic one," Dr Aldis said.

"You're reacting to something that's already happening, and you're ending up chasing the virus around the country. It's obvious that if they don't get enough vaccines distributed, it's going to go around in circles."

Thailand, which has been slow in its vaccine roll-out partly due to shortages, has administered about 19 million doses to date, enough of cover about 13.6 per cent of the population.

The number of active cases has stayed above 200,000 in recent days, overwhelming hospitals, which are also dealing with some 5,000 patients in critical condition.