Heat the vegetable oil in a large pan or wok over medium-high heat.
Add the minced garlic and sliced Thai red chilies to the pan. Stir-fry for about 30 seconds until fragrant.
Increase the heat to high and add the ground beef. Cook for about 5-7 minutes until it is browned and cooked through, breaking it apart as it cooks.
Add the sliced bell pepper to the pan and stir-fry for an additional 2-3 minutes until the pepper is tender yet still crisp.
In a small bowl, mix together the soy sauce, oyster sauce, fish sauce, and sugar. Pour this mixture over the beef and pepper, stirring well to coat everything evenly.
Add the fresh Thai basil leaves to the pan, tossing everything together for about 1-2 minutes until the basil is wilted.
Season with salt and pepper to taste, adjusting for personal preference.
Serve the spicy Thai basil beef hot over cooked jasmine rice.
Notes
Serve with jasmine rice and garnish with extra basil leaves and lime.