Investigators said three speeding pick-up trucks failed to stop at a checkpoint in norther Lampang province, close to Thailand’s porous borders with Myanmar and Laos.

“Police shot out the tyres of the middle car and arrested one Thai national,” Colonel Chairoj Uangpayung, commander of Wiang Mok police station, told AFP.

In his truck they found 3.4 million meth tablets and 20 kilogrammes of “ice” — a purer form of methamphetamine.

Authorities sped after the other two pick-up drivers who escaped, but not before dropping 20 bags of methamphetamine on the road.

“Police have not counted the second batch yet but altogether I think it’s more than seven million tablets,” Colonel Chairoj said.

Investigators estimate the street value of the haul at around $32 million.

Thailand is a major drug market as well as transit route, particularly for “yaba” — meth pills produced in the notorious Golden Triangle region bordering Laos and Myanmar.

The region churns out huge quantities of methamphetamine as well as heroin, opium and cannabis — much of it bound for consumers in Asia and beyond.

While drug seizures and arrests of low-level couriers are common, it is rare for authorities in Laos, Myanmar or Thailand to take down cartel kingpins.

Police data obtained by AFP earlier this month showed Myanmar confiscated a record 98 million meth tablets last year, double the previous year’s haul.

In December, Thai police made a record seizure of pure methamphetamine, seizing half a tonne — worth some $40 million — being transported in an 18-wheel lorry.

A month later they also arrested Laos national Xaysana Keopimpha, describing him as a major drug kingpin, although few had heard of him until his arrest.

Police say Xaysana had links to a number of Thai celebrities and powerful people who are now part of a widening probe.

But experts say most cartel leaders continue to do business with relative impunity and that laboratories in Laos, Myanmar and southern China can easily make up for losses incurred during raids.