The government is seeking to buy another 35 million Covid-19 vaccine doses, taking its total order to 63 million, Prime Minister Prayut Chan-o-cha said on Monday.
Gen Prayut did not say where the extra doses would come from but stressed the government needed to be sure they were safe, had no side effects and were in line with standards set by the country's Food and Drug Administration (FDA).
He said he had instructed the Disease Control Department and National Vaccine Institute to work with the FDA to handle the vaccinations.
The first order of 2 million doses will arrive from China in the next three months, with the government prioritising who should get them, Gen Prayut said.
It also recently signed a deal with AstraZeneca for 26 million doses and the right to produce its Covid-19 vaccine in Thailand, with supplies expected by May. That vaccine will be produced by Thailand's Siam Bioscience with a formula and technology developed by AstraZeneca and the University of Oxford.
"I have also ordered another 35 million doses and most of the population are expected to be vaccinated," the prime minister said.
The Public Health Ministry says the first batch will come from Chinese biopharmaceutical company Sinovac Biotech, with an initial 200,000 doses due to arrive by the end of next month.
The second batch of 800,000 doses will be shipped to Thailand by the end of March, and the last batch of one million doses will arrive by the end of April.
Healthcare personnel and village health volunteers will be offered the first doses.
Gen Prayut also said his government was assessing the situation on a daily basis and ministers were mindful of the economic damage from overly strict containment measures.
"We don't want to lock down the entire country because we know what the problems are, so can you all lock down yourselves?" he said.
"This is up to everyone, if you don't want to get infected just stay home for 14 to 15 days. If you think like this then things will be safe, easier for screening."
Thailand on Monday recorded 745 new coronavirus cases, 729 of them local transmissions, bringing the total since Covid-19 first appeared in January 2020 to 8,439.
One additional death was reported, raising the total to 65, while migrant workers (577) formed the majority of new infections, plus 152 Thai nationals.
The daily increase in case numbers, the largest since the beginning of the pandemic, was expected after Samut Sakhon province reported an additional 541 cases on Sunday. That number is included in yesterday's figures.
The latest death was a 56-year-old man in Bangkok, said Taweesilp Visanuyothin, spokesman for the Centre for Covid-19 Situation Administration (CCSA).
The man died on Sunday, two days after testing positive for Covid-19, and had suffered from numerous underlying diseases before being admitted to hospital on Dec 28. Records showed he had recently travelled to Samut Prakan and the Klong Toey district of Bangkok, he added.
Samut Sakhon recorded the highest number of local transmissions among Thais -- 93 -- followed by Bangkok (28), Chanthaburi (27), Samut Prakan (20) and Rayong (17).
Dr Taweesilp said the number of provinces affected by the latest outbreak rose to 54 after Hua Hin district recorded the first case in Prachuap Khiri Khan.
He reiterated his fear that the number of cases nationwide cases could increase due to people travelling among provinces over the New Year holidays.
Deputy Public Health Minister Sathit Pitutecha said yesterday the CCSA had decided to impose lockdowns in the provinces of Samut Sakhon, Chon Buri, Rayong, Trat and Chanthaburi to stop Covid-19's surge.
The lockdown measures include travel restrictions, with checkpoints to be set up to prevent people in the five provinces from leaving unless they could show it was absolutely necessary, Mr Sathit said.
Meanwhile, Samut Sakhon's public health office late yesterday reported another 470 new infections, which were not included in the national tally reported earlier by the CCSA.
Some 439 of the 470 new infections -- 49 Thais and 390 migrant workers -- were detected by active contact tracing. Of the others, 25 were Thais and six were migrant workers.
Meanwhile, Pol Maj Gen Suvicharn Yankittikul, the Chanthaburi police chief, has been moved to the operation centre at the 2nd Provincial Police Region, pending an inquiry into claims that officers were negligent in allowing illegal gambling dens to operate.