It happened 1-2 times to me in the past that the airline did not have a TM6 form on board, in that case there were plenty available in the airport just before immigration.
Well, that is the worry that many have. The scrapping of TM6 si apparently a temporary measure. Question is: will all IO offices know, some time in the future, that no TM6 were handed out during a certain interval?
I just re-entered today. Frankly this move about TM6 is strange to comprehend. I completed it while still in the air (zero time wasted in the airport), and I was out of the plane and through immigration within minutes literally, including Thailand Pass. Admittedly I was on the special immigration section for transits to CM, CR, Phuket, ... But the Thailand Pass checks were in common for all, very very quick, no queues.
Personally, now that it has been announced that TP will be scrapped from July 1st, I am inclined to think that actually nothing will change re:TM6.