it's a long time since I opened my account but I think your wrong, all banks can open a account if documents are in order,
A friend of mine came from uk in February and opened a account with k bank, he was on 45 days visa exempt, he took his thai girlfriend with him took about a hour ,
He did mention that he was making a big deposit. That may have helped.
my friend has done that for his wife.they have a son together, 5 year visa tests and revue after 2 years 6 months, or something like that. She is still here and working.