I've lost count of the hotel stays that I have had in Thailand. I have left money and my smart devices laying around many times and have never lost a coin nor an item of mine. My wife likes to use the safe, so her items go in there.
Maybe I was lucky but mostly this is just due to the honesty of the staff that we have met. Things may have changed somewhat after covid due to the financial strain that people were under but I still havenot had any items lost.
These two are not indicative of hotel staff, they are exceptions.