Pad thai is Thailand's street food, a one-dish meal peddled on the sidewalks of Bangkok by kiosk vendors who season each order to the customer's liking. The Thai people eat it at any meal -- even breakfast -- washed down with tea, iced coffee, beer or lime juice. Ingredients in the dish vary, but two are integral: rice noodles, fettuccini-like ribbons made from rice flour; and nam pla, a sauce produced by fermenting ocean and freshwater fish in brine and then extracting the liquid. Traditional pad thai usually also includes sweet, chewy dried shrimp, strips of firm tofu, minced garlic, rice vinegar, salt-cured cabbage or radishes, chili powder, cayenne pepper, Chinese chives or scallions, bean sprouts and ground raw peanuts. The King & I prepares pad thai with pork, fresh shrimp or vegetables, including snow peas, baby corn, straw mushrooms and carrots. The restaurant claims that the secret of its insidiously habit-forming pad thai is the sauce, a concoction of nam pla and other condiments, whose recipe the chef will not divulge. Pad thai is a popular menu item at St. Louis restaurants ranging from Shiitake, an upscale pan-Asian hot spot; to Mai Lee, a modest Vietnamese place; to Sukho Thai, a comfortable strip-mall joint on the outskirts of the city. Now, when is someone going to start serving it for breakfast?