A few points from an AK/FD regular, some are more and some are less relevant to the OP's case but might be useful for others:

1) AirAsia is generally very flexible when it comes to their cancellations. They give you the option of a full refund, or to move your flight +-30 days from the original date. I don't know what the threshold, but I remember they gave me the option to rebook when the original flight was rescheduled by an hour or so and it often worked to my advantage. All this is done online and without the need to call.

2) BKK-KBV is a high-frequency route, and I see like 8 flights on a random date. Would none of those flights be suitable for you? If so you can try asking FD to move you to that flight citing that your OTA asked you to contact the airline. You will need to play a bit with Bo to get switched to an operator, but it is doable.

3) I believe GTG used to charge a fee for involuntary cancellations but does not seem to do so anymore (they still do if you want to ask them to change a flight after the cancellation) https://www.gotogate.com/rf/travel-conditions

4) If I was submitting anything to the card company, I would submit the original FD email about the cancellation, their T&C you posted above and the GTG T&C in this post as well as your communications with GTG/Booking.