01 - In a mixing bowl, whisk together the soy sauce, pineapple juice, brown sugar, ketchup, minced garlic, grated ginger, and rice vinegar until the sugar dissolves. Reserve 1/4 cup of the mixture and set aside for basting later.
02 - Place the chicken thighs in a large resealable plastic bag or shallow dish. Pour the remaining marinade over the chicken, seal, and refrigerate for at least 20 minutes, or up to 2 hours for deeper flavor penetration.
03 - Heat a large skillet over medium-high heat. Remove the chicken from the marinade, discarding the used liquid. Sear the thighs for 4 to 5 minutes per side until a golden crust forms and the internal temperature approaches 165°F.
04 - Transfer the chicken to a plate and set aside. In the same skillet, add the sliced red and yellow bell peppers, red onion, and pineapple chunks. Stir-fry for 4 to 5 minutes until the vegetables soften slightly while retaining some crispness.
05 - Return the chicken to the skillet and pour in the reserved marinade. Bring to a gentle simmer, then stir in the cornstarch slurry. Cook for 2 to 3 minutes, turning the chicken to coat evenly, until the sauce thickens to a glossy glaze.
06 - Transfer to a serving platter, spoon the pan sauce over the chicken, and garnish with sliced green onions and toasted sesame seeds. Serve immediately over steamed jasmine rice or cauliflower rice.