I recently purchased, fully refundable, business class seats from Mel to LHR and back. Unfortunately I had to cancel as Thai changed the schedule to one which didn't suit. They accept that the tickets are refundable, but claim it takes 180 working days to process the refund (8 months). Be aware, if you book with them and need to cancel, this is what they will say. There is a Facebook page devoted to trying to get money back from them with 7,400 members. This is not a covid cancellation issue, tickets were purchased this year for flights this year and cancellation was made with 4 months notice. Note, they have $2.2bn in the bank, so cannot claim they can't afford it.