Have you tried the Fascino on Thepprasit? They are opposite that Kaan place. They sell crutches, walkers, wheelchairs, etc.
https://www.google.com/maps/@12.9065165,100.8784395,3a,75y,253.17h,101.27t/data=!3m6!1e1!3m4!1shpeo0VbcmVwLGEFdS44NkQ!2e0!7i16384!8i8192?entry=ttu