Karen L Click asked in another topic:
I have a question on this renewal after 1 year as to space in passport. Once the wp is extended and you go to immigration, is the extension just 'extended' again (a date change notation only) or is it a whole new NonB that will be extended again (2 pages in passport). I have heard it is a date change, but want to be sure as my passport is getting full.
TLDR : Answer Summary
The extension process for a Work Permit (WP) in Thailand involves going to the Ministry of Labor for new dates in the WP without needing additional passport pages, while the Extension of Stay at the Immigration Office will result in a new stamp in the passport but does not constitute a new Non-B visa.