What I hear from people whom I know have travelled to Angor wat say, tickets are best to be purchase in the counter directly. The counter is 4km away where you can pay cash or use card.
Why do you think it's fraud? A lot of people buy tickets online. It's airline tickets or bus tickets. It doesn't matter. I was just as distrustful as you and thought the Internet was a scam, but recently I've changed my mind and you know what helped? A virtual game! In my favorite game I found a site where you can check a players stats https://fpstracker.com/warzone-tracker/ and it turned out to be true