To prepare the sauce, place chiles in a small bowl, and cover with hot water. Let stand 30 minutes. Drain and finely chop chiles.
Place the coriander and cumin seeds in a small skillet over medium-high heat; cook for 1 minute or until toasted. Combine salt and garlic in a mortar and pestle; crush to form a paste. Add the chiles, toasted seeds, lemongrass, 1 tablespoon ginger, and 1 tablespoon shallots, one at a time, until each ingredient is incorporated into paste. Heat 3/4 cup coconut milk in a small saucepan over medium heat. Add paste mixture, and cook for 1 minute. Stir in the peanut butter until smooth. Add sugar, juice, and fish sauce; cook 1 minute. Remove from heat; cool.
To prepare the marinade, combine 1 cup coconut milk and the next 5 ingredients (coconut milk through turmeric) in a large plastic zip-top bag. Add pork to bag. Seal and marinate in refrigerator 45 minutes. Remove pork from bag; discard marinade. Thread pork slices evenly onto 12 (6-inch) skewers.
Place skewers on grill rack coated with cooking spray, and grill for 5 minutes on each side or until done. Serve with sauce.