My Siamese cat Samurai loved thread too, he underwent surgery to remove it from his intestines and the vet almost lost him during surgery. A year later he got a hold of a cone of thread without my knowing and by the time I realized something was wrong it was too late. Our vet is 3 hours away, Sam passed during the drive down :(
My cat Jazz doesn't have a fetish for thread, but I'm not taking any chances, all my thread is in a drawer.