Why not simply use a dictionary to store threadname to thread mapping and just kill from wherever you want.
Dictionary<string, Thread> threadDictionary = new Dictionary<string, Thread>();
Thread myThread = new Thread(() => beginUser(picture));
myThread.Name = Convert.ToString(TableID);
myThread.Start();
threadDictionary.Add("threadOne", myThread);
threadDictionary["threadOne"].Abort();