Stir together the fish sauce, red curry paste, sweetener and chili paste, set aside.
Heat a large skillet and add oil and garlic and red pepper flakes, or chiles if using, heat for a minute. Add the beef and saute on medium-high heat until meat is done. Add green beans and all other ingredients and continue to cook for about 1 minute (longer if using frozen beans) until the beans are tender crisp.
(Can be served over steamed jasmine rice, if not waching carbs!).