Prepare rice noodles by soaking in hot water for 8-10 minutes until al dente, then drain and set aside.

In a small mixing bowl, combine oyster sauce, light soy sauce, dark soy sauce, fish sauce, and brown sugar to create the stir-fry base.

Heat oil in a wok or large heavy-bottomed skillet over high heat until shimmering.

Add the minced garlic and Thai chilies, stir-frying for 30 seconds until aromatics are fragrant but not burnt.

Add the sliced chicken breast in a single layer; sear for 2 minutes without moving, then stir-fry until fully cooked through.

Add the sliced onions and bell peppers to the wok, tossing for 60 seconds to maintain vegetable texture.

Add the prepared rice noodles and the sauce mixture simultaneously.

Toss vigorously over high heat for 2-3 minutes until the noodles are evenly coated and have absorbed the sauce, developing a slight char.

Remove from heat and immediately fold in the basil leaves until wilted by residual heat.

Portion into four equal servings and serve hot.