Prepare the batter: In a bowl, combine the rice flour, all-purpose flour, sugar, salt, turmeric, coconut milk, and water. Whisk until smooth to form your batter.
Cook the crêpe: Heat a cast-iron or non-stick pan over medium-high heat. Add a little bit of neutral-flavoured oil, and once hot, pour in enough batter just to cover the bottom of the pan thinly. Distribute sliced spring onions, bean sprouts, cooked pork, and cooked prawns over the batter. Once the underside has developed colour and is crispy, fold the crêpe in half to form a half-moon shape.
Serve: Serve the crêpes alongside a generous helping of fresh, clean lettuce, picked herbs, and Nuoc Cham for dipping.