If you have a Bangkok Bank ATM, you can pay them via phone or ATM machine...I guess you could pay with any atm card if at a BKK Bank machine...but then I am not sure if you still get the transaction reference number, necessary to quote on your payment confirmation e-mail. Maybe it is printed on the transaction receipt.
The package is a standard EMS cardboard box with nothing indicating the contents.
All this I know from the orders placed by my neighbor.