Heat vegetable oil in a pan over medium-high heat. Combine the chicken pieces with cornstarch in a large bowl. Toss to coat, ensuring each piece is well-covered.
Add the coated chicken pieces and cook until golden brown and crispy, about 4-5 minutes per side. Remove the chicken from the pan and set aside. Remove oil from skillet.
In the same pan, combine the sweet chili sauce, soy sauce, rice vinegar, honey, minced garlic, grated ginger, and red pepper flakes. Stir well and let it simmer for 2-3 minutes until the sauce thickens. Add the chicken and stir.