I finally received my Thai Pass!! What I did differently this time - I submitted a screenshot of my digital vaccine cert, rather than the scanned image of the vaccine cert hard copy (other than the fact that I included the vaccine QR code). And almost instantly, I received the Thai Pass, probably after 3 minutes or so!! Those of you who did not do that previously, you should try! (PS - I'm from Malaysia)
TLDR : Answer Summary
The user successfully obtained their Thai Pass by submitting a screenshot of their digital vaccine certificate along with the vaccine QR code, instead of a scanned image of the hard copy. This change resulted in a quick approval, taking about 3 minutes. They also encourage others who faced issues previously to try this alternative method.