I just recently had my RBC account blocked because they couldn't tell. I was a resident when I went to university 30 years ago. Had the account ever since, as I travel to Canada often. I had to prove my residency was not canadian before they unblocked it.
I have a Canadian daughter, as well as good friends, so I was there often.
Immigration WILL want the 60 day departure flight. Your airline might let you on if you have a return ticket with them because, if Thailand sends you back, you already have a paid ticket with them.
You are allowed to enter if they don't ask. 😅. But if they (either your airline or Thai Immigration) ask you, and you don't have it, they can deny you boarding (airline) or deny you entry (Immigration).
I entered Thailand via Bangkok just over 2 weeks ago from Tokyo. Both the Tokyo check in counter AND Thai immigration in Bangkok wanted to see my departing flight.