Preheat your oven to 375°F (190°C).
In a mixing bowl, whisk together the soy sauce, pineapple juice, brown sugar, ketchup, ginger, garlic, rice vinegar, and sesame oil until well combined.
Place the chicken thighs in a baking dish and pour the marinade over them. Make sure the chicken is well-coated. Cover with plastic wrap and let marinate in the refrigerator for at least 30 minutes, or up to 2 hours for a stronger flavor.
After marinating, remove the chicken from the refrigerator and discard the excess marinade.
Bake the chicken in the preheated oven for 40-45 minutes, or until the internal temperature reaches 165°F (74°C) and the chicken is cooked through, basting halfway through with pan juices.
Remove the chicken from the oven and let it rest for 5 minutes. Garnish with chopped green onions and sesame seeds if desired.
Serve hot with steamed rice and vegetables.