It just goes to show that dealing with what appears to be an easy and reasonable requirement on the surface, is a bit like peeling an onion. There’s just more and more to confront, and in the end you end up crying.
If the purpose is to show that you’re bringing money into Thailand, yes that is logical. If the purpose is just to ensure that you have income and do not become a public ward, the fact that it’s international would seem to be irrelevant.
I have looked at my bank statements and they offer a number of codes, but none that seem to equate with either an international transfer or domestic transfer. I suppose I’ll make a trip to the bank and seek clarification there