You can get a good meal at this inexpensive Vietnamese restaurant if you know how to order, so stick to the dishes you see others eating. Start with a steaming bowl of spicy sweet-and-sour seafood soup (the small order is enough for three or four people) and shrimp grilled on sugarcane. Follow that up with paper-thin pork chops grilled until crisp, and crunchy deep-fried squid served on a bed of shredded lettuce with a tangy dipping sauce. If the line is long, which it usually is, even with a second location around the corner, you may be asked to sit at a table with strangers. Subway: J, M, N, Q, R, W, Z, 6 to Canal St. Other location: 148 Centre St., between Walker and White Sts., PHONE: 212/941-9292.