Can somebody recommend where to get a hearing test in Bangkok that is not a place trying to sell hearing aids, or Bumrungrad, and about the approx costs expected?

Sorry, could you say that again??? Seriously though, you can go to any reputable hospital in bangkok and request a hearing test, you will need to see a doctor to make that request but most of them have the Auditory testing booth required to conduct a hearing test.

I had a hearing test earlier this year at Samitivej Sukhumvit Hospital. They have an auditory testing room as mentioned by midasthailand. I don't recall the price so I guess it was reasonable otherwise I would recall.