In a large mixing bowl, whisk together 1 cup of unsweetened pineapple juice, 1 cup of soy sauce (or tamari for gluten-free), ½ cup of brown sugar, ¼ cup of ketchup, 2 tablespoons of grated fresh ginger, 3 minced garlic cloves, and 2 tablespoons of sesame oil. Reserve 1 cup for basting later.

Place 2 pounds of boneless skinless chicken thighs into a large resealable plastic bag. Pour the remaining marinade over the chicken, ensuring all pieces are well-coated. Seal the bag tightly and refrigerate for at least 2 hours, or ideally overnight.

In a saucepan, pour the reserved marinade and heat over medium heat. Allow it to come to a gentle boil, stirring occasionally for about 8-10 minutes until thickened.

Preheat your grill to medium-high heat, oil the grates, and thread the marinated chicken onto soaked skewers. Grill for about 12-15 minutes, turning every 3 minutes and basting with the reduced glaze.

Transfer the skewers to a serving platter over a bed of steaming white rice. Drizzle any remaining glaze over the chicken and garnish with sliced green onions and toasted sesame seeds.