24 wooden skewers, soaked in water for 3 to 4 hours
Skewer each half chicken thigh with 2 skewers so that they lay flat. Place the chicken in a large shallow baking dish.
Whisk together the orange juice, lime juice, oil, chili powder, and garlic. Pour over the thighs and marinate in the refrigerator 1 to 4 hours.
Prepare a charcoal grill to high heat.
Remove the thighs from the marinade and sprinkle with salt and pepper on both sides. Place the thighs directly over the coals and cook until each side becomes golden brown and slightly charred, about 4 minutes per side. Turn, cover the grill and cook for another few minutes until tender.
Remove from the grill and let rest 5 minutes. Cut the thighs directly down the center creating 2 skewers. Remove the chicken from the skewers and serve garnished with scallions and lime wedges.