I have Thai licenses for both car and m/cycle, expire in 2025..  I have just realised that they both refer to my passport number.  That passport was renewed last year, and I now have a new number.   Is this relevant fro driving in Thailand?  Usually when stopped at police road block, Plod just asks if I have a license.  Never been asked to show it. 

Presumably to change the number to that of new passport would mean new licenses, which will mean a 1/2 day wasted at DLT office.  Should I bother?

I would not bother.

In 10 years never asked to show passport at a checkpoint.

And ordinary policeman have problems to read passports not to speak of number.

You are well identified with photo, name, nationality and birthday.

 

If you have a Thai bank account it is worth to update the passport number.

Old and new passport at hand.

Most people don't and wait until the DL's have to be renewed.

If you have a copy of your passport with you as advised, have a copy of the page where it shows the stamp with the old passport number shown. 

 

I wouldn't bother. I had 2 new passports during my 5 years. Nobody really asks and checks the driving license passport number with actual passport number. If you have plenty of time and like to see the daily officials at work in stone age times do it. You always can tell a great story after.