In a small skillet over medium heat, toast the cumin seeds until fragrant, taking care not to burn. Grind the cumin to a fine powder in a food processor or mortar and pestle.
In a 2-quart saucepan, heat the milk to a low simmer. Add the cheese a handful at a time, whisking to melt between additions.
Add the remaining ingredients, including the ground cumin but excluding the tortillas and vegetable oil, and stir to combine.
Keep the pot at a low simmer, stirring periodically to avoid scorching, for a half hour. Adjust consistency as needed with additional milk.
While the queso is mingling, fill another sauce pot with 4 inches of vegetable oil. Heat to 350° F. Drop the tortilla triangles in, one handful at a time, until crisp and golden. Remove with heat-safe slotted spoon to a towel-lined plate to drain. Sprinkle each batch of chips with coarse salt as soon as they hit the plate. Move the fry oil to a safe place and cover with foil to cool.