Thanks for all your helpful comments even if some went on to speculate as to my wife's motives and those of her friend.
As usual a Thai urban myth perpetuated and applied to inexperienced foreigners, whatever the motivation behind it. I fell for it the first time 10 years ago and that car was put in wife's name. That created serious discord with her family, not her, when I wanted to sell that car and return with wife to Europe in August 2020 during the Covid lockdowns and severe travel restrictions, thinking back then I/we might never return.
It is as I thought ( I've learned alot!). So, armed with the necessary residence certificate from Immigration I bought a car yesterday to be registered in my name.
As to that myth, and being kind to Thais who believe it, it may be that it stems from the very high Thai import customs duty applied to all imported foreign built cars, rather than on foreign built foreigners!