In a large bowl, combine soy sauce, banana ketchup, brown sugar, white vinegar, minced garlic, chopped onion, ground black pepper, paprika, and water. Whisk until the brown sugar dissolves.

Add boneless chicken thighs to the marinade, ensuring each piece is coated. Cover with plastic wrap and refrigerate for at least 2 hours.

Preheat your grill to medium-high heat (about 400°F or 200°C) for 10-15 minutes.

Soak bamboo skewers in water for 15 minutes. Thread the marinated chicken pieces onto the skewers.

Place the skewers on the preheated grill, cooking for 5-7 minutes on each side, basting with leftover marinade.

Check chicken for doneness after 10-14 minutes; ensure the internal temperature is 165°F (74°C).

Transfer skewers to a platter, serve hot with rice and your favorite dipping sauce.