Using a mortar and pestle, pound the chilies, then add garlic cloves and pound into a coarse paste. If you don’t have a mortar and pestle you can crush/chop the chilies with the garlic on a chopping board. Set aside.
In a small bowl, whisk soy sauce, oyster sauce, fish sauce, water and sugar. Set aside.
Coarsely chop the chicken, set aside.
In a wok or a skillet, heat 2 tablespoons of oil over medium heat. Add the paste and fry for 1 minute. add the chicken and fry until cooked through, about 4-5 minutes.
Add the sauce and cook for 2 minutes more.
Turn the heat off and stir in the basil.
Fry the egg: in a pan or wok heat some oil. When oil is hot, crack the egg into the oil. Fry until the edges are browned.
Serve the pad kra pao with rice and top with fried egg.