Prepare the Marinade: Finely chop lemongrass, garlic, and shallot. Mix with fish sauce, dark soy sauce, sugar, and water in a bowl. Add chicken thighs and marinate for 30 mins to 1 hour at room temperature or overnight.
Grill the Chicken: Remove excess marinade from chicken. Lightly oil and grill over medium heat, starting skin side down. Grill for 12-15 mins, turning as needed for even cooking.
Make Nuoc Cham Dipping Sauce: Mix lime juice, hot water, sugar, fish sauce, and optional ingredients until sugar dissolves.
Serve and Enjoy: Let chicken rest before slicing. Serve with vermicelli noodles or rice, vegetables, and Nuoc Cham.
