In a mixing bowl, combine the rice flour, all-purpose flour, baking powder, salt, and black pepper. Gradually whisk in the water until the batter is smooth and well combined.
Add the chopped green onions and cilantro to the batter, mixing until evenly distributed.
In a large skillet, heat about 1/2 inch of vegetable oil over medium-high heat.
Once the oil is hot, add the shrimp to the batter and stir to coat. Using a spoon, drop spoonfuls of the batter with shrimp into the hot oil, being careful not to overcrowd the pan.
Fry the fritters for about 3-4 minutes on each side, or until golden brown and crispy. Remove them from the oil and place them on a paper towel-lined plate to drain excess oil.
For the Nuoc Cham dipping sauce, whisk together the fish sauce, water, sugar, lime juice, minced garlic, and chopped chili in a small bowl until the sugar dissolves.
Serve the shrimp fritters warm with the Nuoc Cham dipping sauce on the side.