I will be flying Bangkok - Phnom Penh with AirAsia. I am used to having a backpack as hand luggage and have Osprey 40l backpack (53 x 33 x 23) that is exactly made to fit the max hand baggage dimensions (56x36x23).
However I have heard anecdotally that AirAsia does not allow backpacks as hand luggage even if they fit within dimensions - which I find hard to believe.
Is it true that AirAsia does not allow backpacks as hand luggage even if they fit within dimensions?