Whisk together the pineapple juice, soy sauce, honey, brown sugar, garlic, ginger, sesame oil, rice vinegar, smoked paprika, and black pepper until smooth.
Place the chicken thighs into a large zip-top bag or shallow glass dish. Pour the marinade over the chicken, coat evenly, cover, and refrigerate for 4 hours or overnight.
Preheat the grill to medium-high heat (about 400°F) and lightly oil the grill grates.
Remove the chicken from the marinade and grill for 5–6 minutes per side until nicely caramelized.
During the final few minutes of grilling, brush the chicken with reserved boiled marinade for extra flavor and a glossy finish.
Continue cooking until the internal temperature reaches 165°F (74°C).
Transfer the chicken to a serving platter and let it rest for 5–10 minutes before serving.
Garnish with sliced green onions and toasted sesame seeds. Serve hot with steamed rice, Hawaiian macaroni salad, grilled pineapple, or roasted vegetables.