In a large bowl, place the garlic, ginger, vinegar, a small amount of sugar, calamansi, tanglad, salt, and pepper. Mix all the ingredients then add the chicken meat. Lightly rub the marinade on the meat. Place chicken in the chiller and let sit. After 30 minutes, turn the meat and let it sit for another 30 minutes. It is not ideal to marinate the meat overnight since the acid of the vinegar will completely break down the enzymes of the meat.
Meanwhile in a saucepan, over low fire, combine margarine/butter and annatto seeds. Stir until the margarine melts and the annatto seeds are well infused and have developed a deep orange color. Turn off heat then add a small amount of salt and pepper to taste.
After marinating the chicken, put several slits on the part near the bone to help with cooking the meat fully. Skewer the meat and cook over hot charcoal grill, skin side down, basting it once in a while. As much as possible do not turn the meat more than twice since the result will be drier meat.
Serve while hot together with steamed rice paired with grilled oysters and sinamak or soy sauce with calamansi and siling labuyo (red chili peppers).