Right.  going from Chiang Mai to Singapore with international transfer at DMK.  All on AirAsia.  Think one hour enough time between arrival and departure?  No checked bags.

Why not phone Air Asia and ask ?

The last time I flew Air Asia was approx. 2011. At a small airport, they would not let us board the plane for the return leg of our flight because we were not there 60 min. before departure. Our tickets said nothing about this, except that it was our responsibility to be there in plenty of time. We had been given no telephone number, e-mail address or website to do that. And the kid at the counter knew that it was his job to keep us off the plane, not to see if he could do anything to get us on. I will never fly Air Asia again.

Just assume you arrive at DMK 15 mins late or the aircraft is slow to deboard. Is 45 mins ok for a connection?  I don't know the answer without checking the Air Asia website but I wouldn't assume the flights will operate on time. 

Book Silk Air and fly straight through. More expensive but worth it to some.

I should have booked AA ,CNX to Kuala Lumpur then SIN.  Not CNX, DMK then SIN.  Y? Immigration at CNX will be much easier than at DMK.  At KL i will only transit thru airport.  Next time i'll probably know more. 

Silk Air one flight/day, arrives night time in SIN, not good for me.  This too, maybe next time.

Some Silk Air flights arrive Singapore1545 but agree late arrival especially somewhere where a hotel room costs a small fortune not ideal. Return trip is around 10k.