Question

Is it possible to reassign thread to a different method, once it has been instantiated. If not, are there alternatives?

Answer 1

Unless the thread has started you could use reflection but the usefulness of such thing is very doubtful. Why not create a different thread instance instead:

var thread = new Thread(Method1);
thread
    .GetType()
    .GetMethod("SetStartHelper", BindingFlags.Instance | BindingFlags.NonPublic)
    .Invoke(thread, new object[] { new ThreadStart(Method2), 0 });
thread.Start();