I have a bank account and come to Thailand every year for 3-4 months, it is so much more convenient to transfer money to pay bills and for spends plus no ATM charges.
I bought a cheap ticket to KL within 60 days,I was asked by Singapore air at UK airport if I had a ticket, but they didn’t want to see it, same at BKK immigration, they asked when I was flying out, but didn’t want to see my ticket.