Thailand's cabinet has granted Premier Prayuth Chan-O-Cha sweeping new powers aimed at curbing Covid-19 that critics fear could be used as a political tool to suppress dissent.

The country is struggling to contain a third wave that has seen a jump of more than 32,000 cases since an outbreak was detected in the capital's nightlife district.

Mandatory mask-wearing and restrictions on daily life have done little to slow the rising death toll, with Prayuth's leadership coming in for criticism for failing to bring the outbreak under control.

Thailand has also been slow in vaccinating its population compared to regional neighbours, inoculating just 1.2 million people since its roll-out started two months ago.

On Tuesday, the cabinet passed a resolution transferring the portfolios of several ministers to the premier, placing Prayuth in charge of laws ranging from the Arms Control Act to the Computer Crimes Act.

The latter is a controversial law critics say broadens the scope of the government's surveillance and censorship powers.  

The move allows Prayuth "the permission, approval, order and command to help in preventing, correcting, suppressing, and deterring an emergency situation", said an announcement in the Royal Gazette, a government website that publishes new legislation.

Authorities said the new powers were aimed at tackling the health crisis.

The leader of the opposition Move Forward Party lambasted Prayuth Wednesday for what it said was his administration's "incompetent" handling of the coronavirus outbreak.

"They can't resolve the political and economic crises with a crisis of people's faith added to the list," Pita Limjaroenrat said. 

"It is time for General Prayuth to stop clinging onto power, which doesn't belong to him in the first place -- return the power to the people."

A former general who masterminded a 2014 coup, Prayuth was voted in as premier after 2019 elections administered under a military-scripted constitution. 

Widespread discontent over the silencing of opposition voices -- coupled with pandemic-spurred economic losses -- later brewed into a pro-democracy protest movement against his government.

At its peak, tens of thousands of protesters took to the streets to call for Prayuth's resignation.

But the movement has slowed this year partly due to Covid-19 but also because in recent months authorities have hit pro-democracy leaders with criminal charges. 

"The bill is not entirely about Covid itself. It's meant to be used as a political tool by the government," said analyst Titipol Pakdeewanich.

"They want to have absolute power like what they had before."