The accident happened at 8.30pm under the flyover connecting Phetkasem road to the downtown district in Tambon Raisom.
The driver, Adinan Laeha, 45, from Narathiwat, and his 18-year-old son were arrested after the drugs were found. The two suffered slight injuries.
The impact saw 26 gold-coloured plastic bags fall from the back of the truck onto the road. Some bags broke open, revealing the drugs inside.
Police checked the back of the truck and found that the truck was transporting a full load of animal feed in white sacks. Police found 15 sacks among the animal feed containing 30 gold plastic bags; each plastic bag contained one kilogrammes of crystal meth.
The two suspects were taken to the Muang Phetchaburi police station for questioning.