there have been harder times with the processing of bookings made on TG's website .... here in Germany t currently works out quite well.
The best way to overcome it is: go to your nearest TG office and pay there by your CC - as long as your web-booking is still "active" (normally about three days) they can process is and dont charge you anything extra.
But note: this works out only when you visit the TG office in the same country where your trip (and ticket), which you booked on the TG-website, starts! Means: dont try it for tickets starting in BKK when you are in any other country!