Pat the chicken dry and cut into 1-inch cubes. Add to a large mixing bowl and toss with Southeast Asia sauce. Let marinate for at least 30 minutes, or refrigerated up to overnight. \nMeanwhile, if using wooden skewers, soak in cold water for at least 10 minutes before grilling. (This will help prevent them from burning). Dry completely before using. \nRemove the ends from the scallions and separate the dark green tops from the lighter green\/white bottoms. Thinly slice the greens and set aside. Cut the bottom portion of the scallions into 1-inch pieces.\nPreheat your grill to medium-high\/high heat. \nRemove chicken from the marinade, reserving any leftover. Skewer chicken and scallion whites onto the skewers, alternating between each and stopping at least 1 inch before the bottom of each skewer. \nPlace skewers on the grill. Brush with any reserved marinade and sprinkle with a pinch each salt and pepper. Grill until char marks appear on one side, about 5-7 minutes. Flip over and brush with any remaining marinade. Continue grilling until well charred on the other side and cooked through, about 3 minutes more. \nRemove to a serving plate. Top with sliced scallions greens and sesame seeds.