SCB will ask you to come in, only to tell you the limit is 50K, and anything more has to be authorized first to activate the transaction for an hour. They currently have no way to cohesively match passport number for foreigners in the same way they match up THAI ID number for locals. On the other hand Bangkok Bank seems to have overcome this.
Do you have a Thai bank account already, I think so if SiamLegal assisted you. Swift transfer to your Thai bank, and perfect/new large denomination bank notes for best exchange rate, don't exchange at a bank, use SuperRich etc.
The illegible certificate from the gym doesn't seem to be a "confirmation letter" from the sports and tourism ministry. The certificate doesn't seem to be a confirmation letter of any kind. Do you have a better quality photo and more documents, specifically a confirmation letter from the tourism and sports ministry that's dated later than 2022 as shown in the certificate?