Cook the rice noodles according to package instructions until al dente. Drain and rinse under cold water to stop cooking. Set aside.
In a large skillet or wok, heat the vegetable oil over medium-high heat. Add the minced garlic and sliced onion, sautéing for about 1 minute until fragrant.
Add the bell pepper, broccoli, snap peas, and sliced chilies to the skillet. Stir-fry for about 3-4 minutes until the vegetables are tender-crisp.
In a small bowl, mix together the soy sauce, oyster sauce, fish sauce, sugar, and sesame oil. Pour this sauce over the vegetables in the skillet.
Add the cooked rice noodles to the skillet, tossing everything together until the noodles are well coated with the sauce and heated through, about 2-3 minutes.
Stir in the chopped basil leaves just before serving.
Serve hot with lime wedges on the side for squeezing over the noodles.