Heat 2 inches of oil in a heavy wok over medium-high heat. Add the scallops, and fry until golden brown on both sides, 2 to 3 minutes. Remove to a plate; set aside.
Pour off all but 3 tablespoons of the oil, and discard. Add curry paste to wok, and fry over medium heat until fragrant, about 5 minutes. Season with sugar and fish sauce. Continue to simmer until quite oily, moistening with the stock.
Return scallops to wok and cook until heated through. Divide between 2 plates. Garnish with lime and cilantro leaves. Serve immediately with rice.