Not true. My 5 accounts (K Bank) are all in my legal western name, copied from my western passport. These accounts at the suggestion / push of the K Bank supervisor were updated in the customer details database to show my pink ID card number.
Two of the 5 accounts were opened at this K Bank branch.
The other 3 K Bank accounts were opened at 3 different locations: CM different branch, Bkk, Pattaya.
As mentioned above all 5 have been updated in the K Bank customer details database to show my pink ID card number. The update of all 5 accounts was done at my local big branch in CM.
Thanks both of you for your opinions. It would appear that banks operate with their own interpretation of the "rules and requirements", just like immigration, local amphurs, DLT etc.
I'll probably try to add my ID card number to my account again when I renew my passport in 2027, since I'll have to register one or the other.