Combine chicken stock, coconut milk, lemongrass, galangal, kaffir lime leaves, and Thai chiles in a large pot. Bring to a boil over medium-high heat, then reduce to a simmer, uncovered, for 10 minutes.
4 cups chicken stock, 14 ounces coconut milk, 2 stalks lemongrass, 3 slices galangal, 3 kaffir lime leaves, 2 - Thai chiles