you are 100% incorrect. I’ve done this 3x when I got a new passport in BKK
You are correct if you mean the initial transfer of visa into the new passport, after that there are no issues and you don’t carry your old passport for the duration of your visa
you do need an invitation letter, that’s the most important document. That should go with gym registration, sports accord accredited, receipt for your training etc. But that’s what I submitted and it was easier and faster than any tourist visa I’ve ever gotten.