Thaw the frozen shrimp in hot water or refrigerator overnight or if using the fresh ones, clean and de-vein. Set them aside. Heat oil in large wok and add garlic, cook for 30 seconds. Throw in the chilli flakes and onions, cook for another 2-3 minutes. Add the shrimp and cook for 5 minutes. Remove and set aside.To the same wok,add the chopped bok-choy and soy sauce and cook till tender for 5 minutes. Mix in the shrimp mixture and salt to taste. Stir and serve with any salad of your choice.