In a medium bowl, combine fish sauce, soy sauce, honey, minced garlic, and minced lemongrass. Add vegetable oil, black pepper, sugar, and fresh lime juice, whisking until fully blended.

Place the chicken thighs into a large zip-lock bag or a shallow dish. Pour the marinade over the chicken, ensuring each piece is well-coated. Seal the bag, removing excess air, or cover the dish with plastic wrap. Refrigerate for at least 2 hours.

About 15 minutes before grilling, preheat your grill to medium-high heat.

Once marinated, remove the chicken thighs from the refrigerator and let them rest for about 10 minutes at room temperature.

Carefully place the chicken thighs on the preheated grill. Grill for 4-5 minutes on one side without moving them.

Once you see a nice brown crust forming, flip them over and grill the other side for an additional 4-5 minutes, ensuring they reach an internal temperature of 165°F.

Once grilled to perfection, remove the chicken thighs from the grill and let them rest for about 5 minutes.

Slice the rested chicken against the grain for easy serving. Garnish with fresh cilantro and serve alongside sliced cucumbers and lime wedges.