Correct.
I returned in July and when Jomtien introduced the new requirement I got my resort manager to resubmit a TM30 for me. He spoke with Immigration who told him that I should go to the Immigration office (with a printout of the TM30 submission) to get a new TM30 receipt to insert in my passport. That is what I did, no fine.
I leave next week (on a re-entry permit) to spend Xmas in the UK. I return on 30th December. I will get the resort manager to submit a TM30 again and I will go to Jomtien shortly afterwards. I need to get another reentry permit so I will attempt to get that at the same time.