Forensic tests on the hair follicles of a truck driver, who had been arrested in Prachuap Khiri Khan's Sam Roi Yot last month for drug use, did not show traces of methamphetamine as suspected, Justice Minister Somsak Thepsutin said.
However, the test conducted on the hair of Sophon Vongsavas did show traces of mitragynine, an active alkaloid in the plant commonly known as kratom.
The minister told media that Mr Sophon had admitted to using kratom -- a plant classified as a narcotic -- to cure gastritis and diarrhoea.
The test had been conducted by the Justice Ministry's Central Institute of Forensic Science at the request of Mr Sophon, who has been seeking justice after being arrested for drug abuse and possession on Nov 13. On that day, Sam Roi Yot district police flagged him down for questioning, before a police officer found one speed pill inside his vehicle.
However, the truck driver's daughter, Nalinee Vongsavas, cast doubt on the arrest after posting a clip on Facebook showing the speed pill being found at a stop where the first police officer had placed his hand earlier. She also pointed out that her father tested negative for drug use in a urine test.
The clip went viral, prompting truck drivers to rally for justice.
Mr Sophon told the press yesterday that he will use CIFS' test to pursue justice.
"I am afraid I have locked horns with the police, but will work towards proving my innocence," he said.
He has also called on the Justice Ministry to launch an investigation.