Place the noodles in a large bowl and add hot tap water to cover. Let stand, stirring occasionally, for 30 minutes; the noodles will become pliable but not fully tender. Meanwhile, in a medium bowl, toss the shrimp with 2 teaspoons of the oyster sauce and 1 teaspoon of the fish sauce. In a small bowl, whisk together the remaining 2 tablespoons each oyster sauce and fish sauce, the sugar, soy sauce and ¼ cup water.

In a 12- to 14-inch wok over medium-high or a 12-inch skillet over high, heat 1 tablespoon of the oil until barely smoking, swirling to coat. Add the shrimp in an even layer; cook, stirring only once, until browned in spots, about 2 minutes; the shrimp will not be fully cooked. Transfer to a plate.

Return the wok or skillet to medium-high and add the remaining 2 tablespoons oil, the shallots, chilies and garlic; cook, stirring, until softened and beginning to brown, 1 to 2 minutes. Add the noodles and toss a few times, then add the sauce. Cook, stirring and tossing, until the noodles have absorbed the sauce and are just shy of tender, about 3 minutes.

Add the shrimp with accumulated juices and the tomato. Cook, tossing, until the shrimp are opaque and the noodles are tender, 1 to 2 minutes. If the noodles are still too firm, drizzle in water 1 to 2 tablespoons at a time and cook, stirring, until tender. Off heat, toss in the basil. Serve with lime wedges.