I don't know why anyone would choose to wait this long for this vaccine.

Lots of reports online of expats over 60 and/or with underlying health conditions, don't we all, getting vaccinated free in Bangkok via the Thailand Intervac site.

Unfortunately if you haven't registered yet there may be a delay, as they currently state: "As the current round of vaccination appointments is full, we will be announcing the new round of appointments for vaccination at https://www.thailandintervac.com. We apologize for all inconvenience".

Still I would expect that you would be vaccinated sooner than the medpark projected timeline, so I would keep checking the website.