Thai soldiers intercepted more than 245 kilos (540 pounds) of crystal meth along the Myanmar border.

The troops seized the illegal haul from suspected smugglers carrying sacks through a rice field in Chiang Rai on Monday.

The Thap Chao Tak Task Force flagged the group for a search at around 10:30 pm, sparking a five-minute gunfight half a kilometre from the Sai River in the neighboring country.

The alleged traffickers retreated back across the Burmese border as reinforcements arrived at dawn.

Authorities swept the area and collected 10 fertiliser sacks filled with narcotics.

Major General Sathit Waiyanon, commander of the Pha Muang Task Force, said: 'I have ordered border patrol personnel to closely monitor the situation and prevent drug traffickers from entering Thailand.'

Chiang Rai province sits along the Golden Triangle, where most of Southeast Asia's meth supply comes from.

The region is found where the borders of Thailand, Laos, and Myanmar meet but it has long been a feral nest of criminal activity, including opium production, meth labs and call centre scam bases.

At the heart of the Golden Triangle lies the Golden Triangle Special Economic Zone (GTSEZ), run by notorious Chinese business tycoon and suspected crime boss Zhao Wei in the Chinese vassal state Laos. Communist chiefs are said to turn a Nelsonian eye to his wrongdoing.

In 2007, Zhao brokered a deal with the Laos government and obtained a 99-year lease to build the zone on a 39-square mile patch of impoverished Bokeo province.

The Chinese businessman claims to be a benefactor as he touts the GTSEZ as a tourist and economic hub designed to bring more income and investments into the country. However, both local and international law enforcement agencies believe it is a front for organised crime, including human trafficking, drug trafficking, and call-centre scams.

International authorities have struggled to take down the gambling empire as the Laos government itself is said to be protecting the GTSEZ, in which it has a 20 per cent stake.