In a large bowl, combine the chicken pieces with soy sauce and cornstarch. Mix well and let marinate for at least 30 minutes.
Heat vegetable oil and sesame oil in a large skillet or wok over medium-high heat.
Add the marinated chicken to the skillet in a single layer. Cook for about 5-7 minutes, stirring occasionally, until the chicken is browned and cooked through.
Add ginger, garlic, green onions, and bell peppers to the skillet. Stir-fry for another 3-4 minutes until the vegetables are tender.
In a small bowl, mix together sweet chili sauce, sriracha, rice vinegar, and sugar. Pour the sauce over the chicken and vegetables, stirring to coat evenly. Cook for an additional 2-3 minutes until heated through.
Season with salt and pepper to taste. Remove from heat and garnish with sesame seeds before serving.