Soldiers seized 600,000 methamphetamine pills and nearly 10 kilogrammes of heroin abandoned by fleeing smugglers, following an exchange of gunfire near the Myanmar border in Mae Sai district of Chiang Rai province on Friday night.
A military patrol from the Pha Muang task force clashed with a drug smuggling gang near a border pass at Pha Mee village in tambon Wiang Phangkham around 10.30pm.
Both sides exchanged fire as the smugglers fled, but no soldiers were injured, Gen Narit Thawonwong, commander of a drug suppression unit in the northern border, said on Saturday.
Soldiers inspected the scene on Saturday morning and found five rucksacks containing illicit drugs.
Three rucksacks contained about 600,000 meth pills, while the other two held 12 packs of heroin each, weighing 9.6kg in total.
Gen Narit said that intelligence reports suggest at least 80 million speed pills and about a tonne of crystal meth are stored near Thailand's northern border, waiting to be smuggled in.
Drug gangs employ various smuggling methods to evade capture, including hiring youths as couriers, using logistics firms and concealing drugs in compartments of vehicles. Illicit drugs are also made in popular forms to appeal to users, said the commander.