But public opinion would need to be gauged first, he said. The idea could materialise if it is backed by scientific research and gains social acceptance.
Krathom is classified as a drug in the 5th category of the Narcotics Act, alongside cannabis and psychotropic mushroom species, but has lighter penalties than those drugs.
Those found guilty of possessing krathom with the intent to sell (more than 10 kilogrammes) are liable to a maximum of two years in jail and a maximum fine of 20,000 baht.
Offenders using krathom are liable to a maximum one month in jail and a 1,000 baht fine.
Mr Chaikasem said he was told by experts that krathom contained many active alkaloids that have both stimulating and sedative effects. However, the alkaloid content found in a plant is less addictive than caffeine in coffee and energy drinks which many people consume every day.
He believes legalising krathom would create benefits than if it continues to be banned as an illegal substance. He said krathom could serve as a solution for people suffering from stress or addicts wanting to stop using drugs.
Mr Chaikasem said he was looking at the possibility of using krathom as a substitute for methamphetamine in the hope of reducing the number of meth addicts, but was not sure if the idea would be possible.
“People who get used to drinking coffee or some kind of energy drink every morning will say they don’t feel refreshed if they fail to consume them. If meth addicts resort to using krathom and feel comfortable, then this is a better way to do it. No depending on narcotic drugs and posing less threats to society,” Mr Chaikasem said.
Commenting on concerns over the wider consumption of the krathom-based drug cocktail known as si khoon roi, or "4x100", once the plant has been legalised, he said it should be noted that krathom leaves alone are “not narcotics” unless they are mixed with cough syrup ― one of the four main ingredients used to make the popular cocktail.
The legalisation of krathom has long been pushed by several sectors of society but it had been opposed by security agencies, he said.
“I grew up in an orchard on the Thon Buri bank [of Bangkok] and experienced widespread use and cultivation of krathom myself. But I’ve never seen anyone [who consumed krathom] turn delirious and violent like other people on other types of drugs.
“We are not encouraging people to consume krathom and want this issue to take its course naturally. Whether using krathom could be useful or help reduce methamphetamine use will depend how people look at it,” Mr Chaikasem said.
Krathom could be used as a less potent, harmful substitute for other powerful drugs to cure addicts in addiction treatment programmes, similar to the use of Methadone to treat heroin addicts, he added.
Mr Chaikasem assigned Dr Anek Yomjinda, director of the Central Institute of Forensic Science, to discuss the proposed legalisation of krathom with the Office of the Narcotics Control Board (ONCB) and other concerned agencies.
Dr Anek said many countries such as New Zealand produced painkillers and antibiotic drugs out of active chemicals found in krathom leaves, while Thailand reported widespread abuse of the plant in spite of its medicinal value.