Prepare pad thai noodles according to packet directions. Set aside.
Sauce:
Place fish sauce, brown sugar, rice vinegar, chili powder and sweet chili sauce and water. Stir to combine. Set aside.
Pad thai noodles:
Heat 1 tablespoon oil in a wok or large frypan over high heat. Add chicken. Stir fry for 3-4 minutes or until chicken pieces are browned and cooked through. Remove from heat. Set aside.
Heat 1 tablespoon oil in the same wok over high heat. Add garlic. Stir fry for a minute or until aromatic. Add shrimp, and stir fry for 2 minutes or until the shrimp changes color. Add spring onions and bean sprouts. Stir fry for a minute.
Add noodles, cooked chicken and sauce. Toss. Heat through. Push noodles to one side of the pan. Pour in egg onto the empty side of pan. Cook, stirring, for 30 seconds. Combine scrambled egg with the noodles. Serve immediately.