A Thai drug smuggler and a police officer were killed in a shootout after authorities intercepted a vehicle carrying a tonne of crystal methamphetamine in the country's north, police said on Wednesday.

The incident followed a routine inspection of a vehicle transporting two men from the Lahu ethnic group in Thailand's northern Chiang Rai province, authorities said.

The "Golden Triangle" region, where Thailand, Myanmar and Laos meet, has long been a hot-spot for drug smuggling, particularly of meth, despite repeated crackdowns.

"The alleged drug smuggler shot a police officer dead, so the police had to defend themselves by shooting a suspect," Tiwapong Pluto, the local chief of the Narcotics Suppression Bureau told AFP.

"The other suspect escaped."

Police seized a tonne of crystal meth following the shootout.

Authorities believe the duo are part of a wider transnational drug smuggling operation that transports meth north to south.

Southeast Asia is awash with meth and authorities netted a record billion pills across the Asian region in 2021, according to a United Nations report.

Neighbouring Myanmar has been in chaos and its economy crippled since a military coup in February 2021, but synthetic drug production in its troubled Shan state was already booming before the putsch.