In a mixing bowl, whisk together fish sauce, soy sauce, and brown sugar until well combined. Add minced garlic, grated ginger, vegetable oil, honey, black pepper, and chili powder. Mix until sugar dissolves.

Place chicken thighs directly into the marinade, ensuring they are fully coated. Cover with plastic wrap and refrigerate for at least 1 hour, or overnight for optimal flavor.

Preheat grill to medium-high heat, aiming for around 400°F (200°C). Clean the grill grates to prevent sticking.

Remove chicken from marinade, allowing excess to drip off. Grill for 5-7 minutes per side until internal temperature reaches 165°F (75°C).

Transfer chicken to a clean platter and let it rest for 5 minutes to redistribute juices.

Garnish grilled chicken with fresh cilantro and serve with lime wedges.