The "normal" visa extension is 1900THB a year, so your paying dearly for it, but if your under 50, not married to a Thai and don't plan to make an heavy investment here, it could be worthwhile. There are benefits with the Elite you should check out.
I would of thought seeing no payment is being made and its a limited time, it would be ok. I have not seen any body being reported for doing this type of work.