Toast split peas, coriander seeds and chiles in a small skillet over medium heat, shaking the pan occasionally, until the split peas turn reddish-brown, the coriander becomes fragrant and the chiles blacken slightly, 2 to 3 minutes. Transfer to a plate to cool for 3 to 5 minutes. Grind in a spice grinder or mortar and pestle until the mixture is the texture of finely ground pepper.
Combine coconut milk, ginger, garlic, cilantro, salt and the spice blend in a shallow glass dish. Add chicken and turn to coat. Cover and refrigerate for at least 30 minutes or overnight.
Preheat broiler. Coat a broiler-pan rack with cooking spray. Place the chicken (including marinade) on the rack over the broiler pan. Broil chicken 3 to 5 inches from the heat source until it is no longer pink in the center and the juices run clear, 4 to 6 minutes per side.
Ingredient noteLook for reduced-fat coconut milk (labeled "lite") in the Asian section of your market.