if he doesn’t have a bank account already his only choice is to show 3 mths income . The visas can now be done online. We are going for the O-A retirement. Includes criminal check, insurance, proof of residence in home country. All sent online to Thai embassy in your country.
We too will be coming to Thailand end of Oct for 6 mths. We purchased a home and need to open a bank account. We are in the process of getting retirement O-A to achieve this. We are only going this route soon as possible as to get the acct. Last year we just left the country and returned. It worked well.