Non-RE = non-immigration re-entry. Stamp is likely fine as it even references the actually visa (p-13) but if you truly want to get it changed you need to go back to the airport she stamped in at
I understand that, however I always ask for the Thai menu and can speak, read and write thai so maybe that's why I haven't encountered it. When it comes to haggling for something, my partner is much better but outside of haggling I've never encountered an issue, nor charged extra. Like I said, I'm aware it happens but it's not as widespread as it's made out to be.
Been living here over 4 years, and have visited here for much longer, never been scammed never been charged farang prices either. I'm not saying it doesn't happen, but it's nowhere near as common as some like to make out.
visa extension is 1900, re-entry is 1000 and at the airport it's + 100 if you don't have the required documents. So if you do it at the airport and don't have the documents required it's 1100
Best to call your airline and ask them. Regardless if it really comes down to needing it. Just book an onwards flight tickets online. Will cost you about $15. It's a legitimate ticket that you're reserving for a couple of days, if searched by anyone it will show in the system you have a ticket.