Poorly written and lazy article from a legal perspective. The article doesn't actually quote the law, it simply references the police interpretation of the law which is not the same thing at all

Try to get an additional one year extension on elite visa for this year... immigration are being more flexible than usual, but you can't change from elite to non O without leaving the country

Online

But don't get stopped by the police before getting the extension....it can get very complicated

It is always better to avoid potential problems by extending before it technically expires, but as the dates fall on a day when immigration are closed, the date for extending is automatically extended to the next day that immigration are open

I have done this process at Chiang Mai a few years ago, so it can be done, but it is possible that they will initially say that you can't change the reason for extension from ED to Retirement (I was told I would have to leave Thailand and get a new visa, which I refused to accept as valid), in which case, just ask to speak to a more senior officer (possibly, it isn't a common procedure, but it is very straightforward in fact). Do make sure that you have a letter from your school confirming that you want to cancel your ED as

@Tod ********

has said and then it's a straightforward process.

My visa expired several years ago...so there is some confusion over teminology

Original tm30 report is valid for the length of your stay in Thailand at the registered address (so need to re-register if you move). Nothing to do with your visa or extension of stay

If you left Thailand and re-entered then yes as you get a new departure card with a new number which needs to be updated. Why it needs to be updated is another question...

Need to file after returning from abroad as this links the new TM6 departure card number received on re-entering Thailand with your existing TM30 registration