I signed up in the google sheets set up by the fansclub at first. That was the way ch3 was to send an email for the preordering.
I did try to order through ch3's site but couldn't get past registration as it won't accept a billing address outside thailand. So i haven't reached the payment part to know whether payment through credit card is allowed. But definitely, DHL is shipping the goods, and DHL has international shipping, so there is hope.
As for those who did not get an email, i usually sourced my dvd boxsets from eThaiCd. That one, i am sure you can choose to pay through credit card. You can also choose to pick from ems, dhl, or snail mail.
I'm going to Bangkok later this week so I'll try to find out more info for you guys.