Regarding a post today from a member who recently extended his stay based on marriage, (in Khon Kaen) He stated that two witnesses were required to accompany him to immigration. A couple of months ago, they told my wife that this was not necessary. I will be checking with them next week to see what answer we get. Mine is due in April.
TLDR : Answer Summary
A member in Khon Kaen recently shared that for his visa extension based on marriage, he was required to bring two witnesses to immigration. However, this requirement seems inconsistent; as per previous experiences, witnesses were not needed for other extensions. A comment also mentioned that witness requirements can vary, often only being enforced during the first application for an Extension of Stay. Immigration may send officers to investigate the authenticity of the marriage, requiring proof through witnesses in different scenarios.