In order to claim input tax credit for GST Malaysia, your Air Asia air ticket must be tax invoice instead of invoice. Air Asia gives the traveller two options to print invoice and/or tax invoice.

You have to print tax invoice on the addon domain of Air Asia - taxinvoice.airasia.com 

 Addon domain for Air Asia Tax Invoice

Enter the detail of booking reference and passenger name
AirTicket 2 
View and Print Tax Invoice for claiming GST Malaysia - Input Tax Credit
AirTicket 3
You can view the procedure inside the attachment.