The truck, carrying fruit and vegetables, was being driven by Chan Sangbarngsai, a Phitsanulok native. It was pulled over at a police checkpoint on the Phitsanulok-Lom Sak road in front of Wang Thong district office at 1.30am.
Police searched the vehicle and found five backpacks hidden in the trailer head that contained 37 kgs of crystal meth and 23 kgs of heroin.
Mr Chan allegedly confessed he had been hired by a drug gang member for 700,000 baht to transport the drugs from Chiang Khong, a Thai-Laos border town in Chiang Rai, to Wang Noi district of Ayutthaya. The gang paid Mr Chan 50,000 baht up front and promised to give him the rest after the job was done.
The drug seizure came after an intelligence report indicated that illicit drugs would be smuggled from Chiang Rai to Ayutthaya through Phitsanulok, said Pol Col Thorntawat Jam-udomchoke, chief of Wang Thong police station.
Police later set up a sting operation by ordering the truck driver to deliver the drugs to an unidentified receiver or receivers in Nakhon Sawan province in the morning but failed to catch them. Pol Col Thorntawat did not elaborate further, saying police would give more details in the case on Friday as they are undertaking further investigations to arrest more people involved.