Stir together the fish sauce, soy sauce, sugar and water in a medium to large bowl and then add the chicken and let marinate.
In a cast iron skillet or large frying pan, heat oil over medium-high heat. Add the onion slices and cook for 2 minutes while stirring.
Add garlic and red pepper to the onions and continue to cook for 30 secs- 1 minute longer.
While pan is hot, add the chicken pieces and cook for about 3 minutes. Next pour in the marinade and cook for another minute.
Remove from heat and then add basil. Stir to wilt.
Cook rice noodles according to package directions while chicken is cooking. Serve basil chicken over noodles and enjoy!
