Whisk mayonnaise, sweet chile sauce, and Sriracha hot sauce together in a bowl.
Place cornstarch in a shallow bowl. Gently press shrimps into cornstarch to coat; shake off any excess.
Heat oil in a deep-fryer or large saucepan to 375 degrees.
Working in batches, cook the shrimp until they are lightly browned on the outside and the meat is no longer transparent in the center, about 3 to 5 minutes. Transfer to paper towels to drain. Put cooked shrimp in a bowl and pour chile sauce mixture over the shrimp. Toss gently to coat.
Line a serving bowl with lettuce leaves. Pour shrimp into bowl and top with green onion.