In a heated wok, combine the cumin, coriander, turmeric, mustard seeds, and pepper flakes and cook, stirring with a wooden spoon, until the mustard seeds pop, about 2 minutes. Add the onion and cook for 2 minutes more, until the onion is soft and translucent. Turn the heat to high and add the okra.
Cook, stirring occasionally, until it is bright and gives slightly when pressed with the spoon, about 2 minutes. Serve with yogurt for dipping.