You'll want to remove all the visible fat from the chicken thighs with a sharp knife.
Mix all of the sauce ingredients together in a small saucepan, and bring it to a simmer over medium-high heat. Once it simmers, turn the heat down low and continue to let it simmer for about 5 minutes.
Set half of the sauce aside (this is important to avoid contaminating your dinner with raw chicken germs)
Fire up the grill and brush a THIN layer of sauce onto each chicken thigh (don't add too much, or the sugar will turn into bitter, black carbon - yuck)
Once the chicken is all done cooking, brush on the reserved half of the sauce.