For the pickled vegetables: Combine the sugar, fish sauce, vinegar and 1 cup water in a saucepan and bring to a boil. Remove from the heat and let cool to room temperature. Transfer the mixture to an airtight container and add the papaya, chiles and carrots. Mix well, seal and let pickle overnight or up to 24 hours.
For the beef: Combine the Kroeung paste, annatto oil, fish sauce and liquid sugar in a mixing bowl with a pinch sea salt. Stir until the salt has dissolved, then add the beef and mix until well coated. Cover and marinate in the refrigerator for at least 2 hours and up to 24 hours.
Heat a grill or grill pan to medium heat.
Thread the beef slices onto the soaked skewers and grill until desired doneness, 2 to 3 minutes per side. Slice the baguettes halfway through, creating a pocket. Fill each one with some pickled vegetables and 2 beef skewers. Pull the skewers out of the rolls and serve.
Recipe courtesy of Luke Nguyen