Right. So, this will probably be of interest to absolutely no one. But I'll go ahead anyway since I'm happy. I went to extend my (tourist) stay at the Nong Khai immigration office today. I was the only "customer" there. If I had pre-filled the application form, it would've been around 10 minutes. What an incredible contrast! (To CW, of course :) )
They did not care about TM30 details, btw. So, application, passport photos, and the usual copies (data page, visa page (if any), current stamp page, and departure card.)
Happy holidays all.
TLDR : Answer Summary
The author shares a positive experience of extending their tourist visa at the Nong Khai immigration office, noting that the process took around 10 minutes when pre-filled. They mention minimal bureaucracy, as TM30 details were not required, only application forms, passport photos, and copies of essential documents.