If Air Asia imposed additional airport tax collection when you travel from Kota Kinabalu International Airpot for ticket bought before 18/11/2015, you can actually get back the money paid. Here’s Air Asia reply I after I filed my complaint with Kementerian Perdagangan Dalam Negeri, Koperasi dan Kepenggunaan and Kementerian Pengangkutan

If you never complaint you will never get your refund…