As others have said - wait until you are in region and apply. Look at the post from Friday in UK. Guy applied in London then flew to Thailand before DTV issued. They obviously saw this on their system. He had had to fly back to UK for application to be processed. A costly mistake.
Norm now with the eGates. I think it would only matter if someone wanted proof. That lad who posted on Friday was asked by the Thai Embassy London to show an exit stamp for his DTV application to continue.
Anonymous participant 666 Good info that you can cancel the Ed after the DTV is issued. Some other visas the previous visa has to be cancelled first. I had this going from O to B.
TM30 is within 24 hours of arrival. I think you mean the 90 Day report which is TM47. This is required if you stay 90 consecutive days in the country. It depends on entry dates and not visa approval dates.