Prepare the Marinade: In a large mixing bowl, whisk together soy sauce, brown sugar, pineapple juice, sesame oil, garlic, and ginger until the sugar dissolves completely.
Marinate the Chicken: Place the chicken thighs into a large resealable bag or shallow dish. Pour the marinade over the chicken, making sure each piece is well coated. Cover and refrigerate for at least 30 minutes, but ideally 2–4 hours for maximum flavor.
Preheat Your Grill or Pan: If grilling, heat your grill to medium-high heat and lightly oil the grates. If using a stovetop, heat a large skillet or grill pan over medium-high heat with a little sesame oil.
Cook the Chicken: Remove chicken from marinade (discard marinade or boil it separately for a sauce if desired). Cook the chicken thighs for about 5–7 minutes per side, until they are cooked through and nicely caramelized on the outside. Internal temperature should reach 165°F.
Rest and Slice: Let the chicken rest for a few minutes before slicing into strips. This helps keep the juices inside.
Serve: Serve over bowls of sticky white rice, garnished with chopped green onions.