In a large skillet or wok, heat the vegetable oil over medium-high heat until shimmering.
Add the minced garlic and chopped chilies to the pan, stirring for about 30 seconds until fragrant.
Add the ground chicken to the pan, breaking it apart with a spatula. Cook for about 5-7 minutes until the chicken is fully cooked and starting to caramelize.
If using, stir in the sliced bell pepper and onion. Cook for an additional 2-3 minutes until the vegetables are tender.
Stir in the soy sauce, oyster sauce, sugar, and fish sauce. Mix thoroughly to combine and let it cook for another 2 minutes to let the flavors meld.
Turn off the heat, and add the fresh Thai basil leaves. Toss quickly until the basil is wilted and fragrant.
Serve the chicken mixture over bowls of hot jasmine rice. Top with a fried egg if desired.
Notes
Adjust the number of chilies based on your spice preference.