BANGKOK - Thailand's government is in talks with U.S. drugmaker Merck & Co to purchase 200,000 courses of the company's experimental antiviral pill for COVID-19 treatment, a Thai official said on Monday.

Many Asian countries are scrambling to lock in supplies of the potential treatment early after they lagged behind Western nations in COVID-19 vaccine rollouts, hit by tight supplies.

South Korea, Taiwan and Malaysia said they are all in talks to buy Merck's potential treatment, while the Philippines, which is running a trial on the pill, said it hopes its domestic study would allow access to the treatment.

They all declined to provide details on purchase negotiations.

Somsak Akksilp, director-general of the Department of Medical Services, told Reuters that Thailand is currently working on a purchasing agreement for the antiviral drug, known as molnupiravir.

The molnupiravir pills, designed to introduce errors into the genetic code of the virus, would be the first oral antiviral medication for COVID-19.

Interim clinical trials indicated it could reduce by around 50% the chance of hospitalisation or death for patients at risk of severe disease from COVID-19.

"We are now working on a purchasing agreement with Merck that is expected to be completed by this week ... we have pre-booked 200,000 courses," Somsak said He said the pills could arrive as soon as December, though the deal would be subject to the pills' approval by the United States Food and Drug Administration and the Thai regulator.

Representatives at Merck's Thailand office were not immediately reachable.

Daily confirmed COVID-19 cases in Thailand fell below 10,000 on Monday for the first time since mid-July. The country has administered 55.5 million doses of COVID-19 vaccines so far, fully inoculating about 31% of the population.

Merck has said it expects to produce 10 million courses of the treatment by the end of 2021. It has a U.S. government contract to supply 1.7 million courses of molnupiravir at a price of $700 per course.

The company has said it plans a tiered pricing approach based on country income criteria.

In the Philippines, Health Undersecretary Maria Rosario Vergeire told a regular news conference on Monday that, "We see we can have more access to this medicine because we have this clinical trial counterpart."

(Reporting by Panarat Thepgumpanat; Additional reporting by Neil Jerome Morales in Manila, Hyonhee Shin in Seoul, Ben Blanchard in Taipei and Patpicha Tanakasempipat in Bangkok; Writing by Kay Johnson; Editing by Kenneth Maxwell and Himani Sarkar) ((Kay.Johnson@thomsonreuters.com; +66-61-417-4587;))