I guess thats one of the negative things about the LCC like Air Asia.
Unlike Thai and BKK Airways, if there is a problem,they haven't back-up aircraft to cover the problem.
I know I would never trust a LCC if I had a connection to make. Just too unreliable,and there are plenty of BMs who have had problems in the past with AirAsia with delays and cancellations.
I'd always pay the extra and use Bangkok Airways.
I guess you have given Air Asia enough chances then Dingo

At least you should get a seat easily to BKK with 1- 2-Go or Nok Air at this time of year.