IN 2 SEPARATE MEDIUM BOWLS, soak bean thread noodles and tree ears in warm water until soft and pliable (about 15 minutes). Drain the noodles and cut into 1-inch lengths; set aside. Drain and rinse off sand from tree ears.
Pinch off and discard hard centers; coarsely chop and set aside. Pound peppercorns, garlic and coriander roots into a coarse paste, or chopped together in a spice mill. Combine pork, shrimp or crab, fish sauce, peppercorn mixture, and 1 teaspoon of the sugar. Add shallots, carrots, bean sprouts, and the reserved bean thread noodles and tree ears; mix together thoroughly. Dissolve remaining sugar with 1 cup water in a bowl.
With kitchen shears, cut rice paper into quarters. Lay one sheet of rice paper with the curved edge nearest to you, on a flat surface. Brush thoroughly with water. Let it sit until it softens into a thin flexible film (about 1 minute).
Mold 1 tablespoon of pork mixture into 1-inch wide by 2-inch long cylinder and put it near the curved edge of rice paper. Fold bottom of rice paper over filling. Fold left and right sides over each end to enclose filling.
Continue rolling until completely sealed. Repeat with remaining filling. Preheat wok until hot. Add enough oil to a depth of 3-inches. Heat to 325F. Add a few rolls and deep-fry for 10 seconds.
Immediately increase to high heat or 375F and deep-fry until crisp and golden brown (about 6 minutes). Remove and drain. Serve wrapped in a lettuce leaf with a mint leaf. Dip into Thai Spring Roll Dip.
THAI SPRING ROLL DIP: Combine sugar, water and vinegar in a saucepan over medium-high heat; boil until reduced to 3/4 cup of liquid. Remove from heat and stir in the fish sauce and chile flakes. When cooled, transfer to a dipping saucer and mix in coriander and peanuts. Makes about 24 rolls with sauce.