Some Embassies will need to see the 500.000 Baht to be in the account for 6 months
Read the Embassy website for their requirements, There you can also be lucky to find out how long time the Embassy normally need to process the application.
Remember that asking for additional documentation can reset the clock to zero
You need to document 12 monthly transfers of at least 65.000 baht all done on time and not missing any, before you can change to the monthly transfer system.
It is you who try to mislead the OP to believe that the Embassy will provide reason for the cancellation.
It is still stated on the Embassy website that they will NOT provide any reasons about the reason for cancellation, so it is silly to think you will get a reason.