The invitation letter can be requested after registration.
For that purpose, please send a request to the local chair, i.e. Prof. Mahardhika Pratama, email@example.com with the following information:
Name (as it appears on your passport) and mailing address;
Your registration confirmation number;
If you are the author of any papers accepted for the conference, please provide the title, if you are a speaker, please provide the title/topic of your speech.
Those requesting a letter should allow up to one week to receive it, as requests are handled in the order they are received.