Prep the noodles: If using dried rice noodles, soak them in warm water for 20–30 minutes until pliable but still a bit firm. If using fresh rice noodles, separate the strands.
Drain well before cooking.
Make the sauce: In a small bowl, whisk soy sauce, oyster sauce, fish sauce, sugar, dark soy (if using), and lime juice. Taste and adjust. You want salty, savory, slightly sweet, and bright.
Chop aromatics: Mince garlic and chilies, and slice the shallot.
Pick the basil leaves from stems. Slice bell pepper and trim green beans if using.
Heat the pan: Set a large skillet or wok over medium-high heat. Add 1 tablespoon oil and swirl to coat until shimmering.
Cook the chicken: Add chicken in an even layer.
Let it sear for 1–2 minutes without stirring, then break it up. Cook until no longer pink and lightly browned. Season with a pinch of salt.
Transfer to a plate if your pan is crowded.
Sauté aromatics: Add another tablespoon of oil. Toss in garlic, chilies, and shallot. Stir-fry 30–45 seconds until fragrant.
Don’t let the garlic burn.
Add vegetables: Stir in bell pepper and green beans. Cook 2–3 minutes until crisp-tender.
Combine chicken and sauce: Return chicken to the pan. Pour in the sauce and toss to coat.
Let it bubble for 30 seconds so the flavors meld.
Add noodles: Add drained noodles and toss vigorously. Use tongs to lift and fold, coating every strand. If noodles seem stiff, splash in 1–2 tablespoons water to loosen.
Finish with basil: Turn off the heat.
Add Thai basil and toss until wilted and glossy, about 20–30 seconds.
Serve: Plate hot with lime wedges. Garnish with extra basil or scallions if you like.