thank you, my youngest, was a chewer of shirts. This is the FIRST year that he is NOT chewing on shirts. He just turned 12. He shows some Asperger's traits but only has a diagnosis of sensory integration disorder. The treatment of that when he was 5, which still continues, is what several people say has helped keep him from needing more supports, testing etc.....
It is NASTY but they are unable to stop unless they have another option. they NEED that oral stimulation. With something to chew my thank you can do almost anything and with-o well, the kid can barely walk and breathe. It helps him block out other sensory stuff and is soothing to him. Instead of arguing over it, I bought his shirts at yard sales and thrift stores. This year he has gotten to pick some more expensive shirts and has been taking good care of them. Not sure what caused the change, don't really care, just happy it is here.
Occupational Therapist (OT) supply places have other things for kids to chew on. A chewy necklace would work for thank you as long as he could remember what he did with it. I also was careful to not buy flame retardant clothing or things with any kind of screen print design near his face and wrists. I have no idea what those would do to a kid but they sure are not designed to be eaten.
Scolding/punishing will only make this much worse as it is a way for them to handle stress. I strongly recommend that you have him evaluated for sensory issues by an Occupational Therapist (OT). Schools have these but they only look at how things impact his time at school. Private OTs look at how they impact all of his life and in my opinion and my experience they are FAR FAR more comprehensive.
There are 2 awesome books you should read, both by Kranowitz. First is The Out of Sync Child which describes the sensory issues in detail and the second is The Out of Sync Child Has Fun. If money is tight get the first from the library or ask if school has a copy you can borrow (here parents can check books out as well as kids from the school library) and buy the Has Fun book. Why? Well, the Has Fun book has all kinds of activities to help provide the sensory stimulation your child is wanting. It has hints and tips to make that affordable and honestly, it is one of the most fun books we have ever had. The activities were ones that all my kids enjoyed, not just thank you.