Police stopped a Chiang Rai-registered Toyota car driven by Kaew Khamchan, 50, of Chiang Rai's Mae Sai district at the checkpoint for a search.
Four suitcases were found in the car's boot. Found in the suitcases were 400,000 methamphetamine pills and 2kg of ice.
The woman was charged with having illicit drugs in her possession with intention to sell. An investigation was underway to establish her connection to a drug ring.