Place each chicken thigh between 2 sheets of heavy-duty plastic wrap, and flatten to 1/4-inch thickness, using a rolling pin or flat side of a meat mallet.
Combine sugar and next 3 ingredients; rub over chicken.
Grill chicken, covered with grill lid, 2 to 3 minutes on each side or until done.
Remove from grill, and cover with aluminum foil to keep warm.