Good work.
The on-line is not "on-line".
It purely produces a application form which you complete, print and take with you on Dec 7. It does give you a registration identifier.
Make sure you have the correct photos, Embassy very strict on this.
The Embassy website recommends a shop in the Embassy Sathorn Hotel. It is not far away. Go up the alley, LHS towards the end.
Cash payment not accepted at Emmbassy. Take a card.
All pretty painless but the Embassy is a sterile environment, do not expect to see Chuckles the Clown.????????