In 3- to 4-quart slow cooker, layer beans, chicken thighs, garlic, chiles, cumin and salsa.
Cover; cook on Low setting 7 to 8 hours.
About 15 minutes before serving, heat oven to 350°F. Wrap tortillas in foil; heat in oven about 15 minutes or until warm. Meanwhile, place all topping ingredients in individual serving dishes.
Remove chicken from slow cooker; place on large plate. With fork or potato masher, mash beans slightly to thicken sauce. Shred chicken with 2 forks; return to slow cooker and mix with bean mixture to moisten.
Have guests place warm tortilla on serving plate. Spoon about 1/2 cup chicken mixture onto tortilla; top with desired toppings. Fold sides of tortilla over filling; secure with toothpick.