As here in EUR more and more places are wanting to see that QR-code and there is also an app for those who check that the code is really OK, for a tourist not from here life is getting more difficult. And what wonder of surprise-indeed it does work, mine was checked in Spain, France (for every long train ride). The usual touristy fora like tripadvsior etc. give advice to USAers wanting to visit EUR and how to transfer their own vaccine data into such a code.
From very recent other posts on other Thai fora I gather that the Thai now even trust this EU-system enough to just accept it.
BTW-the code will also automatically vanish or become invalid if you were not vaccinated but just tested after while.
Meanwhile there also seems to be a small blackmarket for selling (up to several 100 eur are said) false codes-police have already arrested several medical assistents and some of these codes have been made invalid. Whereas the vaccinations are all free.............