1. Heat the broiler or light the grill. In a medium bowl, combine 1 tablespoon of the fish sauce, 1 tablespoon of the sugar, 2 cloves of the garlic, and the oil. Add the chicken, toss, and then thread each strip onto a wooden skewer. Broil or grill the chicken until just done, about 2 minutes per side.
2. In a small bowl, combine the remaining 4 tablespoons fish sauce, 1 tablespoon sugar, and 1 clove garlic with the red-pepper flakes, vinegar, lime juice, and water. Set this nuoc cham aside.
3. In a pot of boiling, salted water, cook the vermicelli until just done, about 9 minutes. Add the bean sprouts during the last minute of cooking. Drain, rinse with cold water, and drain thoroughly.
4. Put the pasta and bean sprouts on a platter and top with the cucumber, herbs, and chicken skewers. Pour the nuoc cham over all and sprinkle with the peanuts.
Wine Recommendation: The high acidity, citrus and mineral flavors, and slight sweetness of a German riesling are the perfect foils for the sweet and savory taste of this dish. Try a young kabinett from the Mosel region.
Notes: Asian fish sauce is available at Asian markets and many supermarkets.