Keep mine in a bank book sleeve, and has worked for decades, keeping dry & looking new. My 'bag' is water resistant/proof, and my yellow book is in a sealed waterproof plastic thingy.
If ever caught in Typhoon or Tsunami, I could always put my PP in with my yellow book, as a bit roomy.
Some of the comments are just silly, people always losing their possessions, or keeping 'paper' items in sweaty shirts or going swimming at SongKran with them.
Depending where you hang out, most don't need to carry, unless at the tourist ghettos, where corrupt folks may hang out.
As stated, just safer with me, on or in car nearby. Hotel room/safe, big NO ... IMHO. Front desk, maybe, but then one might forget when checking out, then not realize, till checking in for that int'l flight ... oops.