yea so whenever I’ve needed proof of onward travel I go to Qatar airlines website. Go thru the booking process like normal and when it comes to time to pay just pay $10 for the booking on hold. They send you a confirmation that looks similar to a flight booking
I went to the embassy with my passport, paid a fee($50 usd), got a certificate of residency then took that and my passport to Bangkok bank and they gave me a bank account.