The ticket requirement just means you need to print the email confirmation (or show physical ticket) that has the actual long ticket number from the airline, which proves the ticket has been paid for. What they don't accept is the 6 digit alphanumeric confirmation number issued by the airline (the one you use to check in for your flight or make flight changes) since that doesn't prove the ticket was ever paid for or issued. The 6 digit confirmation number could just mean you have a ticket on hold that will be canceled because you never paid for it. For example, Bangkok Airways will send me an email with the 6 digit confirmation number when I call them to make a reservation that I want to pay for in person at the ticket office or at 7-Eleven, but they don't send me an email with the actual e-ticket number on it until I make the payment and the ticket is issued.

Assuming you bought your ticket online, once a ticket is paid online and the ticket has been issued, the airline or booking website such as Expedia, sends a final version of your itinerary that includes the ticket number. That's why often when you buy a ticket online, you first get an email confirmation that only has the 6 digit confirmation number before the ticket is issued, then another email a few minutes or hours later that will include the full long ticket number along with the 6 digit confirmation number. The reason they still include the 6 digit confirmation number is that is what you use to check in to your flight either online or at an airport kiosk, but the super long ticket number is the actual proof the airline issued a ticket to you. That's the email you want to print out.

If you don't get the visa in advance, you run a small risk of immigration asking to see your return ticket and denying you since technically you are required to prove you are exiting the country before your visa exempt period is finished.

The consulates and immigration people won't accept an itinerary without an actual confirmed ticket number, which you only get after paying for the ticket. Before you pay for the ticket, all you can get is the 6 digit booking reference number that all airlines issue which is NOT an actual ticket number. So a "on hold" itinerary won't qualify for a visa. Your best option is to buy a full fare fully refundable ticket on a major airline then canceling the ticket to get a full refund.