Combine sweet potatoes, onion, curry powder, ginger, and garlic in a 4- to 5-qt. slow cooker. Sprinkle chicken with salt and add to the slow cooker. Drizzle with oil. Cover and cook on High until the chicken registers at least 165°F on an instant-read thermometer, 3 to 3½ hours.
Add bell pepper, snap peas, and coconut milk to the slow cooker. Cover and cook on High until heated through, about 10 minutes more. Top with cilantro and serve with lime wedges.