Why was a TM30 required for my tourist visa extension in Chiang Mai, and how can I prepare for it in the future?

I went to Chiang Mai Immigration Office, by the airport for a 30 day extension for my tourist visa. They were asking everyone to produce a copy of their TM30, even sent some back to their hotel for it. In over ten years, in various offices, I have never been asked for a TM 30 for a visa extension. I know it is mandatory to have a TM 30 but assumed they had means of checking without actually asking. Luckily, there is an office that will produce a TM30, presuming your hotel has applied for one, and a photocopy shop next door. Just wasted a lot of time, as I had to rejoin the queue each time. I know for next time.