If using a motor cycle taxi, just use the crash helmet they have.
if no have, use his one. ( been there done that )
if he says no, get a different motor cycle taxi.
Who cares if it's smells a bit. much better than your head smashed open in an accident.
Had one last week, taxi rank pattaya Thai second road intersection.
No crash helmet.
ok I not use you,
it ok no police.
I want cash helmet. one was found under the seat, on one of the other taxi guys bikes.
Sorted.