Place a rack in top third of oven; preheat to 400°. Stir coconut milk and curry paste in a 2-qt. baking dish to combine (or, use a medium skillet if that’s what you’ve got). Add lemongrass, ginger, and garlic. Season chicken with salt (hold back a bit since curry pastes often have a lot of salt). Place in baking dish and spoon some liquid over. Bake, occasionally spooning liquid over, until chicken is browned, tender, and cooked throughout (the joint should be reasonably easy to flex), 60–75 minutes.