Apologies, probably should have left mention of TOT out of the thread title.
My experience of the local post is seriously mixed. I doubt half the postmen are fully literate, we regularly get post for other sois with the same number, plus the occasional random 'can see no possible reason for error' deliveries.
We have a post box on the wall but some postmen insist on just perching the mail in the lattice of the folding security gate, where it often falls out and ends up on the pavement. TOT bills were always hit and miss, we got disconnected twice, hence switching to e-service. Mail from HSBC in Singapore takes weeks to arrive if it does at all, credit and debit cards regularly go missing, HSBC often end up sending a second by DHL. Stuff that's supposed to be recorded delivery and signed for never is. This is in Hat Yai city, not Nakhorn Nowhere.
The PO Box option would remove the middleman, though not remove the issue if it is indeed criminal intent in the sorting office rather than incompetence/illiteracy in the postman.
Good luck trying to bring the Post Office to book, but I suspect it will be a futile endeavour.