A Shan State man from Myanmar was arrested after troops intercepted his pickup truck and found 300kg of crystal meth on Wednesday night.
Pol Maj Gen Wichit Wongsang, commander of the Pha Muang Taskforce, said his officers set up a checkpoint on the bypass near Chiang Rai's Mae Sai district between the Thai-Myanmar Friendship Bridge and Ban Nam Jam village in Tambon Pong Pha.
The troops said they saw a pickup slow down and make a U-turn before it reached the checkpoint so they chased after it until the driver lost control and drove off the road.
Wichit said the driver managed to flee into the roadside forest but his passenger, Sam, also Shan, was arrested.
The authorities later learned that the fleeing driver was identified as Nattapol Thongkham, 34.