Was it a personal bank account, savings or checking typing account? Workation means you work for a company remotely, but actually you are just a contractor/freelancer? Can you explain your company work relationship a bit? You need a letter stating that you can work remotely and specifically in Thailand. Do you hold a Bangladesh passport? I'd contact the embassy and try to glean exactly where your application failed in their eyes.
likely your application was cancelled, not rejected. Cancelled application it's usually due to biodata error on your main passport page, a rejected application is usually due to insufficient documents.
Strange that the airline asked, typically that's immigrations job. Can't you show a bank account app with the cash in it? 10K baht is pocket change, you really don't have it handy?
In all likeliness you'll be given an under consideration stamp for a period of time, possibly 30 days. If you bought a reentry permit after you've been given that stamp then you would have to return by the date on the under consideration stamp to get your full year inked in.