Heat oil in a large skillet or wok over medium-high heat. Add onion, garlic and chilies; sauté until fragrant, about a minute. Add pork and salt; cook, breaking up with a spoon, until no longer pink inside and crisping at edges. Add green beans and cook, stirring frequently, until crisp-tender but still bright green, about 2 minutes.

Meanwhile, whisk together soy sauce, fish sauce and brown sugar. Pour into pan and stir to coat pork and beans. Taste and add a pinch of crushed chiles if more heat is desired. Stir in basil leaves and serve with noodles or rice.