At 6 July 2017 I did fly with Air Asia from Don Muang Airport, and I (and many other people) was a bit unpleasantly surprised. Be aware that Air Asia has changed their check-in procedure. First you will have to go to a SELF CHECK-IN booth. As there are only 4 booths per check-in row you will understand that there is a cue of people. As most people (like me) are not used to use a SELF CHECK-IN there is a Air Asia service lady helping you. You will get a boarding card and if you have luggage you will get labels for your luggage. After that if you have luggage (like me) you will have to cue again, now to drop-off your luggage. This is also self-service. But again as nobody is yet used to that there is a Air Asia service lady helping you.
The bottom line is you will have to cue twice and you will have to do it all by yourself. Now I understand that an airline is trying to lower the costs with self-service but due to the way it is set-up at Don Muang Airport it will result in more time consuming check-in for people with luggage.