In a medium saucepan, heat 2 tablespoons of sesame oil over medium heat. Sauté 2 teaspoons of grated fresh ginger and 2 minced garlic cloves until fragrant, about 1 minute. Stir in ⅓ cup low-sodium soy sauce, 1 tablespoon rice vinegar, ¼ cup brown sugar, ¼ cup ketchup, and ½ teaspoon smoked paprika. Combine 1 tablespoon cornstarch with 2 tablespoons of cool water, add it to the saucepan, and simmer while stirring for 3-4 minutes until the marinade thickens.

Once the marinade has cooled, reserve ½ cup for later. Pour the remaining marinade over 2 pounds of boneless, skinless chicken thighs in a large bowl or resealable bag, ensuring they are well coated. Seal the bag, removing excess air, or cover the bowl tightly. Refrigerate for at least 1 hour, but up to 4 hours for best flavor.

About 15 minutes before grilling, preheat your grill to medium-high heat, aiming for around 375°F (190°C). Lightly oil the grates with a paper towel dipped in vegetable oil.

Once the grill is preheated, remove the chicken from the marinade and place it on the grill. Grill each piece for about 4-6 minutes on one side, then flip and baste with the reserved marinade, cooking for another 4-6 minutes. Ensure the internal temperature reaches 165°F (75°C).

After cooking, carefully remove the chicken from the grill and let it rest for a few minutes to redistribute juices. Serve warm on a platter with sides like jasmine rice or grilled vegetables.