Prepare noodles according to package directions (soak if dried, separate if fresh). Drain and set aside. In a small bowl, whisk together all sauce ingredients: oyster sauce, dark soy sauce, light soy sauce, fish sauce, and brown sugar.

Heat 1 tbsp of oil in a wok or large skillet over high heat until smoking lightly. Add chicken in a single layer and sear for 2-3 minutes per side, until a golden-brown crust forms and it's cooked through. Remove from wok and set aside.

Reduce heat to medium-high, add the remaining 1 tbsp of oil. Add minced garlic and sliced chilies and stir-fry for 30 seconds until fragrant. Add green bell pepper strips and julienned carrots and toss for 1-2 minutes until crisp-tender.

Add the noodles to the wok, followed by the sauce. Toss everything to coat the noodles. Add the cooked chicken back to the wok and toss to combine.

Turn off the heat and immediately add the fresh Thai basil leaves. Toss one last time to allow the basil to wilt from the residual heat. Serve immediately.