In a medium bowl, dissolve sugar and salt in hot water. Add vinegar and veggies. Let sit at room temp until ready to eat.
In a small bowl, combine the mayonnaise and red curry paste. Set aside until ready to eat.
In a large bowl, combine rice vinegar, soy sauce, sesame oil, 5 spice powder, brown sugar, red curry paste and peanut butter until it comes together in a thick paste. Add the ground beef and cilantro. Stir to combine until well combined.
Portion the meat and form 4 patties. Grill or cook on a frying pan.
Generously sauce the bun with the red curry mayo, then layer on the burger, top with the pickled veggies and fresh cilantro. And dig in!