Place the cornstarch in a large ziplock bag. Add chicken to bag and shake well to coat chicken pieces.
Beat the eggs in a medium bowl. Place the flour in a separate large ziplock bag. Working in two batches, dip the coated chicken into the beaten eggs, and then dunk into the flour. Repeat until all chicken is coated.
Heat 2 Tablespoons of oil in a large non-stick skillet, over medium-high heat. Working again in two batches, add one half of the coated chicken to skillet. Cook and stir until thoroughly cooked, browned and crispy; about 12 minutes. Remove chicken from skillet and place in a bowl. Tent with foil and set aside.
Heat 2 more Tablespoons of oil in the skillet and repeat cooking process with remaining chicken. Transfer this chicken to the plate with the other chicken. Cover and set aside.
Carefully wipe out the skillet clean. Add the remaining 1 Tablespoon of oil, bell pepper, onion, pineapple and garlic. Stir and cook until bell pepper and onion are slightly tender; about 5 minutes.
Add the cooked chicken back to the skillet with the bell peppers, onion and pineapple. Pour in the sweet Thai chili sauce and gently stir to combine everything. Cook another minute or until mixture is heated through. Serve immediately and enjoy!