In a large mixing bowl, combine soy sauce, banana ketchup, brown sugar, and white vinegar.

Add minced garlic, chopped onion, ground black pepper, salt, and paprika. Whisk until well blended.

Cut chicken thighs into bite-sized pieces and add to marinade. Mix until chicken is coated, cover, and refrigerate for at least 2 hours.

Preheat grill to medium-high heat (around 400°F) for 20 minutes.

Thread marinated chicken onto soaked bamboo skewers, leaving space between pieces for even cooking.

Grill skewers for 5-7 minutes on each side, basting with leftover marinade.

Remove from grill, let rest for 5 minutes before serving.