Combine first 6 ingredients in a small saucepan. Bring to a boil; cook until reduced to 1/4 cup (about 2 1/2 minutes). Remove from heat; cool.
Combine soy sauce mixture and the chicken. Cover and marinate in refrigerator for 1 hour.
Heat a large grill pan over medium-high heat.
Thread 6 chicken cubes and 5 green onion pieces alternately onto each of 4 (10-inch) skewers. Brush kebabs with the soy mixture. Coat pan with cooking spray. Place kebabs in pan, and cook 4 minutes on each side or until the chicken is done.