Add the scallion, garlic, hot pepper, ginger, lime juice, soy sauce, vegetable oil, brown sugar, thyme, salt, black pepper, allspice, and nutmeg to the bowl of a food processor. Pulse a few times to chop everything up a bit, and then process until it turns into a chunky sauce with a consistency similar to runny salsa.
Measure out ½ cup of marinade and put it in the fridge in an airtight container for cooking later. Add the chicken and the remaining sauce to a large bowl and toss well to coat. Cover the bowl with plastic wrap and refrigerate at least 2 hours or up to 24 hours.
20 minutes before you want to cook the chicken, soak 6 wooden skewers in water (to help prevent them from catching on fire). Preheat grill to medium-high.
Spray the skewers with cooking spray, then thread the chicken onto them. Grill the skewers until the chicken is fully cooked, about 5 to 7 minutes per side, brushing with the reserved marinade if they look dry. When the chicken is done, there should be no pink in the center, and it should reach an internal temperature of 165F.
Serve the chicken skewers topped with any garnishes you like, along with Creamy Cilantro Lime Ranch for dipping.