In a large mixing bowl, combine the diced chicken thighs with 1 tablespoon of vegetable oil, garlic powder, and a sprinkle of salt and pepper. Toss until evenly coated. Sprinkle the cornstarch over the chicken and mix thoroughly.

Heat 3 tablespoons of vegetable oil in a large skillet or wok over medium-high heat. Once shimmering, add the coated chicken in batches. Cook for 5–7 minutes until golden brown and crispy, stirring occasionally. Remove and set aside on a paper towel-lined plate.

In the same skillet, add more oil if necessary and heat. Add sliced bell peppers and sauté for 3–4 minutes until tender but crisp. Add minced garlic and cook for an additional 30 seconds until fragrant.

Return the cooked chicken to the skillet, toss with sautéed bell peppers, then add green beans, sweet chili sauce, and sesame oil. If using, add crushed red pepper and ginger. Stir until evenly coated and heated through for another 2–3 minutes.

Remove from heat and give a final stir. Serve immediately over rice and enjoy the vibrant colors and flavors.