In a large mixing bowl, combine cubed boneless skinless chicken thighs with vegetable oil, garlic powder, salt, and pepper. Let it marinate for about 10 minutes.

Sprinkle cornstarch over the marinated chicken and mix to create a light coating.

Heat a wok or large skillet over medium-high heat and add vegetable oil.

Add the chicken to the hot oil in batches and cook for about 5-7 minutes until golden brown.

In the same pan, add more vegetable oil if needed and toss in sliced bell peppers. Stir-fry for about 3-4 minutes.

Add the minced garlic and optional ginger, stirring for about 30 seconds until fragrant.

Return the cooked chicken to the pan, followed by the steamed green beans. Drizzle in sweet chili sauce, sesame oil, and crushed red pepper. Stir gently to combine.

Serve the stir fry hot over a bed of steamed rice or on its own.