I maybe wrong but I think A class is a restricted F ticket at less than the full F fare. Either way when trying to book an F ticket for next January from HKG to BKK I can only get the full F Fare offered

. I have flown this route a couple of years ago and the fare I paid then was about half what I am being offered now.
BTW I am doing this booking from my home in London and I have spoken to the London office and they say they will only book the full fare and the cheapest option is to go online (which is where I started).
Any tips of how to get a reduced fare would be most appreciated.
Thanks.