AirAsia doesn’t prohibit hiking backpacks in their Cabin baggage page anymore. So as long as your backpack fits the dimensions (56cm x 36cm x 23cm) it should be fine to bring on board.
That’s what they say:
Important notice:
- Boxes and hiking backpacks are not considered as cabin baggage and must be checked in.
- Multiple items that are strapped, wrapped or tied together will not be counted as one piece of cabin baggage.
Credit:stackoverflow.com‘