I could not get the ATA online. They told me to go to a city close to the border where I was planing to cross and apply there. There will be some agencies to help you out too.
For me the problem was that via email the openly told me that id have to pay 100% deposit (if I remember correctly) instead normal 40% only cos Im foreign. I thought that when they can so easily manipulate the rules they might as easily not give me the deposit back when back so I decided not to go to Mongolia.
One member here did it thios way and payed normal deposit. His fellow Chinese riders helped him out tho

As for the driving licence, add me on wechat (jaro11111) I have a contact who can help you do your international licence in the Philippines. I didnt do it through him but I know a guy who did and it went smoothly