the best situation is to call the visa issuing authority and hand the phone to the bank officer - or carry printout or links to Thai websites that mention the rule
they must be really going to remote areas or Banks that are not having any well trained or English educated speakers nor any expat customers and wonder why they go there while there are 100s of branches all over . Each mall has a dedicated floor with almost all banks opening branches in every main city of every 76 province of Thailand