In a bowl, combine the ground chicken, chopped shrimp, and scallion. Add the corn starch, salt, fish sauce (if using), sesame oil, and ground white pepper. Mix well until all ingredients are fully incorporated. Set aside.
To wrap the wontons, place a wonton wrapper on your palm. Add 1/2 tablespoon of the chicken and shrimp filling to the center of the wrapper.
Dip your index finger into water and run it along the edges of the wonton wrapper.
Fold the wrapper over the filling, then pinch the edges together to seal the wonton tightly. Make sure there are no openings and the wonton is securely enclosed.
Heat cooking oil in a wok or deep frying pan over medium-high heat. Once the oil is hot, carefully add the wontons in batches and fry until they are golden brown and crispy.
Remove the wontons with a slotted spoon and drain them on a paper towel-lined plate to remove excess oil.
For the dipping sauce, mix together the Thai sweet chili sauce, lime juice, chopped cilantro, and white sesame seeds in a small bowl.
Serve the hot wontons with the dipping sauce on the side, or enjoy them plain.