If you use the services of a licensed Bangkok based private investment advisor, they can assist assist in your acquiring this visa, or so I have been told.
i have heard of someone being denied a visa due to overstay stamp, but it was a while ago. Visitors should respect the terms of their visas and avoid such situations.
Well, most businesses do levy a charge for their services or else they can't remain in-business. Whether or not you decide to engage their services or try doing it on your own, is your choice. Good luck Paul!