Looks easier than Issan as there you need numerous photographs of the family in front and outside of the houses. A map with directions from immigration to your house and 2 witnesses. This was the case in Khon Kaen. Regardless, marriage extensions are more difficult than retirement extensions by far.
it takes 2 days to get your Visa. You submit your paperwork and pick it up the next day. I did it at Vientiane and Suvanaket. That was 10 years ago. I have heard you need to make an appointment now. You can’t just show up. I’m by no means an expert so confer with more people