@Stuart ********
I've never done it. but it's very well documented.
Do you really think they can't update their systems to relate an existing visa to a new passport number?
The PDF isn't the visa. The visa is in the database.
When we're all going through the auto gates at BKK (my last exit was through an automatic gate), visa stamps and pdf hard copes become 100% irrelevant.
Most Thai embassies in western countries are already only issuing e-visas.