Do I need proof of leaving Thailand after 45 days or can I show proof after 75 days?

Depends where you are flying from. For Canadians you just need a return ticket per the embassy website (and I have this confirmed by email that date is not important). On YYZ check-in I was asked how long I was staying (my return date was > 45 days). I was also asked by Thai immigration how long I was staying, but wasn't asked for POOT.

Thai immigration did not ask me but the airline did. When I took out the printed copy of the exit flight information, they barely even glanced at it 😂 Thankfully, I only spent $10 renting the flight ticket from a site.

Ask your airline

Not sure why you couldn’t find the answer, but sometimes the search function isn’t brilliant on Facebook.

Your question is asked every single day.

The answer remains the same. Immigration almost certainly won’t ask for a flight/ticket out. Your airline quite probably will. Call them and ask their policy. Some even don’t know about the change to 45 days and may insist on a ticket out within 30 days. We can’t tell you what they’ll ask. You may find they don’t even ask at all. Flip a coin. Heads they ask. Tails they won’t. If it lands on its side immigration may grill you for your intentions and insist you have a ticket out (the last part is pedantic and almost certainly won’t happen).

All depends on the airline you will use. Better ask them. You can always book a fake ticket on day 44.

There is a small chance that Thai Immigration will ask, there is a greater chance that the airline will ask at check-in.

You might be ok but there’s a decent chance that you won’t.