Put the dried shrimp in a bowl and cover with hot water. Let stand for 30 minutes. Drain and finely chop the shrimp.
In a large skillet, melt 3 tablespoons of the butter. Add the shrimp, scallion whites and sliced chile and cook over moderate heat until the scallion is softened, about 2 minutes. Add the corn kernels and stir well. Add the sugar and fish sauce and cook, stirring occasionally, until the corn is crisp-tender, about 5 minutes. Stir in the remaining 1 tablespoon of butter and the scallion greens, season with salt and serve.