Mix marinade. Place thighs in a gallon ziplock bag, pour in marinade. Marindate at least 3-4 hours. Make another batch to create sauce, no garlic or ginger.
With second batch of marinade, place in small pot. Mix cornstarch with small amount of water. Bring marinade to a boil and add cornstarch mixture to thicken.
Grill thighs. Slice and pour sauce over chicken.