Microwave the green beans according to the package’s directions.
Meanwhile, in a large skillet, melt the butter on medium. Add the flour and thyme and cook, stirring, until golden and fragrant, about 2 minutes. Stir in the milk and bring to a boil. Simmer, stirring, until thickened, about 2 minutes.
Stir in the green beans and season to taste with salt and pepper. Transfer to a serving dish. Just before serving, top with the chips.