In a large bowl mix together 2 tbsp of the olive oil, the oyster sauce, garlic and ginger paste, soy sauce, rice wine vinegar and salt and pepper. Take half of the mixture and pour into a smaller bowl. Add the water to the smaller bowl, mix and set aside.
Add the chicken pieces to the larger bowl and toss the chicken around so that each piece is coated in the mixture. Let it sit and marinate for about 10 minutes.
In a large skillet, heat the remaining 1 tbsp of olive oil. Add chicken pieces to it and cook until the chicken is cooked through and it starts to slowly brown. Remove chicken from skillet and set aside.
Add onion to the same skillet and fry, add additional oil if needed to the skillet. Once the onion is translucent, add the peppers and snow peas and the oyster sauce. Stir and cook for a couple minutes, the sauce will begin to thicken. Add the chicken to the skillet and toss everything together.
Serve over rice and garnish with basil.