There were three options for COVID-impacted bookings with THAI;
1. try and seek a refund. 2. take a voucher for the value you paid for your flights, and use it at a later date. 3. keep your tickets 'open dated' for use at a future time.
So you have ended up with option 3 kind of by default.
I deliberately sought option 3 as my ticket already had my ROP Gold upgrade applied to it and the other other two options would certainly see this lost. I also have (kind of) re-booked and am happy enough. THAI doesn't fly directly to Auckland since the pandemic so things have been a bit tricky.