From the Washington DC embassy: 10) What type of COVID test is needed?
Upon checking in at the departure airport, the approved applicant is required to present a medical certificate with a laboratory result using RT-PCR test indicating that COVID -19 is not detected. Such COVID-19 test result must be issued no more than 72 hours before departure.
if I was reading it correctly, you have to be one of the 46 approved countries for 21 days before you come to Thailand and be able to do the one day quarantine.
All is still uncertain but you are correct in saying your multi-entry visa will be just that muti-entry. once borders open up, I think that you will need to deal with returning requirements like insurance and possibly vaccine proofs. All is still very fluid on what will happen and when it will happen. Just putting my two cents in. Sorry if I stepped on my toes.
not certain but I think you can enter with a tourist visa and then change to a Thai Elite visa. You may need to get an extension while you with for the Elite visa process to be completed. I hope that others in the group will correct me if I gave incorrect info.