Add chicken, coconut milk, onions, tomato paste, garlic, ginger, cumin, turmeric, garam masala, coriander, curry powder, bay leaves, cinnamon stick, salt, and pepper to a slow cooker.

Cook on High until chicken is no longer pink in the center and the juices run clear, 2 to 3 hours. An instant-read thermometer inserted into the center should read at least 165 degrees F (74 degrees C). Remove and discard the bay leaves and cinnamon stick. Shred the chicken.