Add the remaining 2 tablespoons of vegetable oil to the wok. When the oil is hot, add the chiles, shallots, garlic and belacan and stir-fry over high heat until aromatic, about 2 minutes. Add the shrimp and stir-fry for 1 minute. Add the rice, reduce the heat to moderate and cook, stirring, until heated through, 3 to 4 minutes; sprinkle the rice with water as necessary to keep it moist. Stir the oyster sauce, soy sauce, white pepper and sugar into the rice. Stir in the scrambled eggs. Transfer the rice to a platter or bowl, garnish with the scallions, cilantro and pickled mustard greens and serve.