Coat outdoor grill rack with nonstick spray; heat grill.

Mix spice powder, sugar and salt in small cup. Rub spice mixture over chicken. Grill 5 minutes per side over direct heat. Move to indirect heat and grill, covered, 15 to 20 minutes untip instant-read thermometer registers 160°F, or juices run clear.

Meanwhile, coat bok choy and mushrooms with nonstick spray. Grill over direct heat for 10 to 15 minutes, turning once.

Stir soy sauce and rice vinegar in small bowl; spoon some over vegetables and chicken. Sprinkle chicken with sesame seeds.