More than 500 importers of illegal health products have faced legal action over the past year, says the Food and Drug Administration (FDA).
Secretary–general Paisarn Dunkum said the Consumer Protection Police Division has investigated importers of illegal and dangerous health products and arrested more than 500 of them while 250,000 online advertisements were also banned.
"The police are gathering evidence to arrest more," Dr Paisarn said on Sunday.
Forty per cent of complaints submitted by consumers stemmed from claims in social media advertisements which overstated the benefits of food supplements, medical equipment, cosmetics and drugs.
He said an advertisement for an electric body massaging machine was found to have misled readers into believing it was a quality product with a high value. It was advertised with a heavily discounted price to entice customers, yet its drug licence had not been issued.
"There are many online drug stores which are engaging in illegal conduct," Dr Paisarn said. "Drugs cannot be legally sold through online stores because their effects might put the lives of consumers at risk.
"It is impossible to investigate every online product. Drugs are a sensitive issue because, if the product is fake or expired, it may cause death to consumers."
Consumers who want to avoid buying fake drugs should ensure the product has an FDA registration licence which guarantees its status, he said.
If consumers find they have bought poor quality drugs, they can file a complaint with local police or the FDA. The FDA can then track the seller. He said the best option was to buy drugs through drug stores.