In a mixing bowl, combine the cilantro roots, ginger, garlic, lime leaves, red curry paste, soy sauce, canola oil and white pepper. Stir well.
Add the minced white fish and yard long beans. Cover and let refrigerate for 1 hour to marinate.
Shape the mixture into 1-inch balls then smush them into little pancakes with the palms of your hand. Place them on a baking sheet lined with parchment paper.
In a large wok over high heat, heat 2 cups of canola oil for deep frying. When the oil is hot, reduce the heat to medium. Working in batches of 15 fish balls at a time, use a slotted metal spoon to carefully drop the fish balls, one at a time, into the hot oil and deep-fry until they turn brown and oil starts to sizzle, 2-3 minutes.
Use the slotted spoon to transfer the balls to a plate lined with paper towel to drain off the excess oil. Repeat until all fish balls have been cooked.
Serve Thai Fish Cakes with sweet chili sauce.