I had a Siamese that loved to chew my thread on my sewing machine. One day she was acting like she felt bad, then the next morning was hiding like cats do when they are very sick. I found a little amount of thread she had thrown up. She had chewed the thread on my machine and swallowed it One end was caught on her tongue, and the other was wrapped around her intestines. She had to have emergency surgery and upwrap the thread from her intestines. The thread almost sawed them in half. It was nip and tuck, but the vet was able to save her. Another hour, and he probably wouldn't have done so. Boy, was I careful of thread after that. I've heard that Siamese like to do that. She was the only Siamese I've had that did that, but watch out for your cats.
Susan