Boil chicken breast in 2 cups of water until cooked (about 10 minutes). Shred or dice into small pieces.
In a large pot, heat 1 tbsp oil. Add garlic, ginger, and green chilies. Sauté for 1 minute.
Pour in chicken stock and water. Add shredded chicken, sweet corn, soy sauce, vinegar, black pepper, and salt. Simmer for 5 minutes.
Stir in the cornflour slurry (mix cornflour + water before adding). Cook on low heat until slightly thickened (~3-4 minutes).
Slowly pour the beaten egg into the soup while stirring gently to form silky ribbons.
Turn off heat. Garnish with spring onions and coriander. Serve hot with chili sauce or lemon wedges!