In a mixing bowl, combine soy sauce, brown sugar, water, minced garlic, grated ginger, and 1 tablespoon of cooking oil to create the marinade.
Place the chicken thighs in a shallow dish and pour the marinade over them, ensuring they are well coated. Marinate for at least 30 minutes, or up to 24 hours in the refrigerator, turning occasionally.
Heat the remaining tablespoon of cooking oil in a large skillet over medium heat. Add the marinated chicken to the skillet, discarding any leftover marinade.
Cook the chicken for 5-7 minutes on each side, or until fully cooked and the marinade has reduced to a glaze.
Remove the chicken from the skillet and let it rest for 5 minutes on a cutting board before slicing. Serve warm.