iin that my son walks around the house in womens thongs?

Buy him a burka. He can wear whatever he wants under it!

I think he is testing like a typical adolescent. But it is your home & it is not unreasonable to expect some sense of decorum - I mean walking around in a woman's g-string with your teenaged schlong and sac flopping about - come on!

Your home your rules. But don't forget what a perfect kodak moment this is. Get some pictures to preserve for posterity. You may want to share them with grandchildren some day!