Maj Gen Banjerd said the clashes followed the deployment of combined teams of regular soldiers and rangers to border areas on suspicion that drugs would be smuggled across the border during the Songkran festival.
At about 4am on Sunday, one of the teams spotted a group of 10 couriers, each carrying a backpack and an individual weapon, in an area north of Pa Kui village in tambon Thaton of Mae Ai district and told them to stop for a search.
The group opened fire at the authorities and a battle raged for about five minutes.
A second clash, lasting 10 minutes, erupted at 5am when the soldiers moved in to clear the area, pushing the couriers back across the border.
Four teams of soldiers and rangers then combed the area at 7am.
The bodies of two drug couriers were found with a backpack and a fertiliser sack, containing altogether 100,000 methamphetamine pills. A hand grenade was also recovered near the bodies.
Earlier on Saturday, seven drug smugglers were killed in a clash with soldiers of the Phua Muang Force in Mae Fa Luang district of Chiang Rai province. Altogether 700,000 speed pills were seized.