In a large skillet, heat the olive oil over medium-high heat. Add the wax beans, shallots and garlic, and cook, tossing as needed until golden brown, 4 to 6 minutes.
Reduce the heat to medium and add the lemon juice, thyme leaves and red pepper flakes. Season with salt. Cook until the beans are just tender, while still retaining a bite, 5 minutes.
Stir in the arugula leaves and cook until just wilted, 1 minute more. Transfer to a platter and serve.