In a blender, combine the garlic, cilantro, fish sauce, vegetable oil, hoisin sauce, coriander, kosher salt and pepper; blend until smooth.
Arrange the pieces of chicken in a large, shallow glass or ceramic dish.
Pour the marinade over the chicken and turn to coat the pieces thoroughly.
Cover and refrigerate overnight.
Light a grill.
When the coals are covered with a light gray ash, push them to opposite sides of the grill and set a disposable drip pan in the center.
If using a gas grill, turn off the center burners.
Arrange the chicken on the hot grate above the drip pan and away from the coals, skin side down.
Cover and grill for 40 minutes or until the skin is crisp and the meat is cooked through. Transfer to plates and serve with Thai chile sauce.
MAKE AHEAD The marinade can be refrigerated overnight.