In a large mixing bowl, add the sliced beef along with Thai soy sauce, brown sugar, and vegetable oil. Combine all ingredients well and set aside to marinate for at least 15 minutes.
If using fresh noodles, gently unravel them with your fingers until they are separated. If they are difficult to separate or slightly dry, soak them in warm water briefly to loosen them up.
In a medium mixing bowl, combine oyster sauce, Thai soy sauce, Thai black soy sauce, fish sauce, brown sugar, and water. Mix thoroughly until all ingredients are well incorporated and the sugar has dissolved completely.
Heat one tablespoon of vegetable oil in a wok over medium-high heat until hot. Add marinated beef slices and cook for about 1-2 minutes on each side or until cooked through; then remove from heat and set aside.
In the same wok, add another tablespoon of vegetable oil over medium-high heat. When hot, toss in minced garlic and sauté for about 30 seconds until fragrant before adding thinly sliced Chinese broccoli; sauté until it wilts slightly.
Push all ingredients to one side of the wok and add whisked eggs to the other side; let sit for about 10 seconds before scrambling them with a spatula until fully cooked through. Remove everything from the wok and set aside.
Add prepared noodles back into the hot wok and spread them evenly across the pan surface; char them lightly for approximately 30 seconds before pouring in your mixed sauce. Toss everything together thoroughly until noodles are coated evenly and caramelized; finally fold in cooked beef, broccoli, and scrambled eggs before serving immediately.