So:
On 17 March, Thai cancelled my flights and I phoned and was granted a refund. Obviously it has not come through yet.
Just about 50 days ago, I filed a chargeback, with Revolut, which goes via MasterCard, showing proof of the cancellation granted refund (which Thai sent to me by email).
I spoke to Revolut to get an update since we got to their/MC deadline past 45 days and the money was still not back in my account, and they informed me that Thai rejected the chargeback on the basis that they have granted the refund but that it will take 180 days. Thai responded in the last few days before the deadline.
Revolut/MasterCard is not siding with me as a result, HOWEVER, they have said that they will respond today (Monday) by saying that the answer is not good enough, because if they accept it, we lose the case and yet the refund may not appear and then the case cannot be revived again. This means that from today, they will have another 50 days to respond (Revolut apparently considers 50 days rather than MC's 45.)
So now it is a waiting game again, and I won't have another update until 11 August.
(180 day mark from 17 March is 13 September 2020, though their email saying they actually processed the refund came in mid-April, so if they are counting 180 days from then, that's mid-October.)