If the property is part of your rental business, it will be an issue. If it is just for your living purposes, then should not be. The letter you need can be easily got on ChatGTP.
There was a recent rejection of a Thai bank account you may have read. The issue was sending his salary to that Thai account giving the impression he had business/employment ties to Thailand. A Thai bank account is fine to show for the 500k.Important to ensure its' activity is inline with DTV guidelines.