An agent I used in Bangkok altered the place where we intended to marry from our town (which I had put on the form) to the province so that we had the choice of any amphur. We actually went to our own amphur. Last September (2018) we went into their one stop shop (having no appointment). Form was printed and we filled it in. Told to fetch two witnesses. Mrs was asked if she wanted to change her surname? I didn't even have to speak. Didn't see a registrar. No charge.