The money at the hotel...NO WAY...
I'm sorry but I don't buy that anybody would have trusted a relative stranger, regardless if you had sex the previous night, with over $6500 on the dresser while going to have breakfast! That part just didn't make any sense. No way anybody does that, dumb or not. Nobody even trusts people they trust with that kind of money laying around.
The other aspect was that Louise just entrusted Thelma with the money...for...checks notes...NO REASON WHATSOEVER! Seriously, no reason was given at all. Probably because there's no way to think of one. Michael Madsen brought Louise the money, so he wasn't going to steal it. He could have helped provide protection to it from any overnight burglars as well. And you're on the run for murder...so instead of keeping the most valuable thing you have in the world with you or your boyfriend...you just hand it over to your ditzy/slutty friend?! No way. They should have came up with something else.