Heat the vegetable oil in a large skillet or wok over medium-high heat.
Add the minced garlic and chopped chilies, stirring for about 30 seconds until fragrant.
Add the ground chicken to the skillet, breaking it apart with a spatula. Cook until browned and cooked through, about 5-7 minutes.
Stir in the sliced red bell pepper and green beans, cooking for an additional 3-4 minutes until the vegetables are tender-crisp.
In a small bowl, mix together the soy sauce, oyster sauce, fish sauce, and sugar. Pour this sauce over the chicken and vegetables, stirring well to combine.
Remove the skillet from heat and fold in the fresh Thai basil leaves until just wilted.
Serve hot over cooked jasmine rice.