Preheat the oven to 350 degrees . Lightly butter a 9-inch casserole dish. In a bowl, toss the ham, cornbread, peas and thyme; transfer to the baking dish. In the same bowl, beat together the milk, eggs and yolk and salt. Pour into the baking dish. Let stand for 15 minutes.
Bake until the custard is just set in the center, 40 to 45 minutes. Let stand for 10 minutes before serving. Serve with a green salad.