Then be aware of the fact that recently they changed the rules of their tickets sales and some class do NOT have FREE baggage anymore. You can buy baggage up-to 24hr before leaving, but after that it costs 300 THB per kg. In that case it might be cheaper to buy an all new ticket.
Of course you can just use carry-on baggage as long as you do not have more as 7kg, your baggage is not to big and your baggage does not contain things that can not be taken as carry-on.
I assume Air Asia will be happy with this new promotion of Nok Air as now there is no reason anymore not to fly with Air Asia. So here I come Air Asia!