In a mixing bowl, combine fish sauce, soy sauce, honey, minced garlic, minced lemongrass, vegetable oil, black pepper, sugar, and lime juice. Whisk the ingredients together until well blended.

Place the chicken thighs in a zip-lock bag or shallow dish. Pour the marinade over the chicken, coating thoroughly. Seal or cover it and refrigerate for at least 2 hours.

Preheat your grill to medium-high heat (around 400°F/200°C) and clean the grates with a paper towel dipped in vegetable oil.

Remove chicken from marinade, letting excess drip off. Grill the chicken for about 4-5 minutes on each side until cooked through (internal temperature of 165°F/74°C).

Let the chicken rest for a few minutes before slicing against the grain into strips.

Arrange grilled chicken on a platter, garnished with cilantro, cucumber slices, and lime wedges.