After I got hinted to a list of municipality creation in last year, Google helped me to find the same for 2005, hidden deep inside thailocaladmin.go.th.
Unlike last year, in 2005 there were much less entries in this list, only 5 thesaban tambon upgraded to thesaban mueang, and 13 TAO upgraded to thesaban tambon. While the upgrades have all been announced in the Royal Gazette already, there were apparently three announcements for the creations, which I already listed earlier as still pending announcement. All there were signed in June 2005, but one from August was published in September. I start to doubt these are really not yet published, and more think they might be simply wrongly indexed in the Gazette database - which would be odd as unlike the historic announcement no-one needs to type the title anymore, everything can be done with copy-and-paste.