Cut off the base of the bok choy stalks; discard. Separate the stalks and leaves. If the stems of the bok choy leaves are large, chop finely. Wash the leaves and stalks; drain in a colander.
Heat the oil in a large skillet or saucepan over medium-low heat. Stir in the green onions, mushrooms, garlic, crushed red pepper, salt and black pepper; cook, stirring often, 5 minutes. Stir in the bok choy and coconut milk; cook, stirring until the leaves are tender and stalks are still crunchy, 3-6 minutes.