, in 19 years, they've only asked me for my passport once, and I voluntarily hand it over along with my driver's license at every checkpoint. But no police officer, high-ranking or otherwise, in Pattaya, Bangkok, Chaiyaphum, or Surin, has ever taken an interest in my 90 days. It should be noted that the fine isn't necessarily 5,000 baht, but 5,000 baht is the maximum amount you could be fined.
, i've never heard of police officers checking to see if you've submitted the 90-day notification during a check. But, since T.I.T. is a law, never say never.