BREAK UP CLUMPS OF RICE by gently rubbing between the palms of your hands into a large bowl. Over medium- high heat, preheat wok until hot. Add oil; tilt wok to coat sides. When oil is moderately hot, add salt and the optional shrimp paste, stir until fragrant or for 5 seconds. Immediately add rice and quickly stir-fry, pressing and poking at clumps of rice until all grains are separated, without browning rice (about 3 minutes). Season with sugar, soy sauce and oyster sauce. Stir-fry until each grain is evenly coated (about 1 minute). Push rice to sides of wok. Add beaten egg mixture to center of wok, and allow to cook, lightly beating eggs in center only (about 1 minute). Toss together with rice. (Small flecks of egg will appear interspersed in the rice.) Add shrimp, barbecued pork, chicken, peas, lettuce, and green onions; toss and stir until mixed and heated through and lettuce is wilted (about 2 minutes).