Police seized more than 1.5 million meth pills and 305kg of crystal meth in a crackdown on drug networks in northern Thailand.

Provincial Police Region 5 said the massive illegal haul was seized in two separate drug busts amid clashes between soldiers and suspected drug syndicates in neighbouring Laos.

The first case involved a 'suspicious car' driven by Natthawut, who claimed he was returning from a trip to the Phu Chi Fa mountains in Chiang Rai on May 5.

Police inspected the vehicle at a checkpoint in Lampang, but found no illegal items inside. However, they said they continued monitoring its movements as the road was a known drug-running route near the border.

Officers found that Natthawut had taken a detour into the Mae Prik District. They also saw a blue Toyota van following close behind.

Police intercepted both vehicles at a checkpoint and discovered 13 sacks containing 305kg of crystal meth.

All seven involved - identified by officials as Thamolwan, Anuwat, Thanakrit, Chawalit, Thanawin, Somsak, and Natthawut - were detained. They allegedly admitted that they were hired to deliver the drugs from Chiang Rai to central Thailand.

Just a day later, police acting on a tip-off about a drug shipment pulled over a truck driven by Ekkarak in Chiang Rai.

They found eight sacks containing 1.57 million meth pills inside.

Ekkarak reportedly confessed he had been hired by a man named Narongchai to take drugs to clients in Uttaradit and Sukhothai.

Narongchai was later arrested at a checkpoint in Mae Sai while trying to flee through the border.

Police Lieutenant General Krittapol Yisakhon, commissioner of Provincial Police Region 5, said: 'We observed that drug traffickers have shifted their routes from northern Thailand to the northeastern border, which has triggered tensions among minority groups in Laos.

'They seem to be trying to avoid the heavily monitored corridor by relocating their production and smuggling operations.However, we anticipate they will be returning to the northern route due to problems they are now facing in the northeast.

'As a result, we've instructed our officers to tighten security in the region, especially in Chiang Mai and Chiang Rai.'

Thailand's northern border lies along the notorious Golden Triangle - an area where its borders meet with Laos and Myanmar.

The Golden Triangle is a major centre for illegal drug production, with meth supplies surging as powerful Chinese-run crime syndicates thrive in the area.

Poverty, political instability, and corruption have enabled the illicit trade to thrive for decades despite efforts to curb it.