The 15-minute pre-dawn gunfight followed a tip-off to the Pha Muang task force that a large batch of narcotics would be smuggled into Thailand via Ban Chalor 9 area.
The rangers staked out the area starting December 7 and at 5.30am on December 10 spotted a group of 20 to 30 men carrying backpacks and travelling on foot.
The rangers reportedly told them to stop for a search but they instead opened fire, resulting in the brief gun battle.
The rangers found five dead bodies and 19 makeshift backpacks made of fertiliser sacks, each containing 100,000 “yaba” pills.