I have a piece of paper that says I was vaccinated. I just uploaded the images. To be fair my vaccine letter is in English and Thai.. But I don't have a card or a cerficate.
Your options will vary by time time you need the additional 20 days. I think land borders will open and they may do away with Thai Pass, that will make visa runs easier. You may wish to visit a neighboring country while you are here. Come, hang-out 2+1 months, go Cambodia 3 weeks, fly home through BKK, not a bad option.
print EVERYTHING before coming. last time I came (mid February - Phuket) I had forgotten to print some document. It really complicated things. Just print out everything.
Could take a camel. Go south by horse until you find a bunch of people speaking Spanish. Take boat to Africa (I don't recommend swimming), get camel go East. If you run into people speaking Chinese, you've gone to far.
I have heard rumor that ED (not erectile dysfunction) visas are will cause you issues at immigration when returning to Thailand. You can get a no-class/no-test ED visa but you will always have to worry about immigration officers testing your Thai language skills when trying to re-enter the country. Otherwise you will need to really study and really go to class.
I have been wondering about Muay Thai ED visa.. It would be uncivilized to test that skill-set in the Airport.