you will be fine on a Multi Entry Tourist Visa, after having stayed abroad for a little longer than six months. But it is questionable if you can stay for another 6 months on visa-exempt entries. Immigration will check your TOTAL stamp history of the recent 365 days! Better get a multi entry TR Visa. Apply for it ahead of 4 weeks before December 9th, and send an email kindly ask them to issue the visa as close as possible to this flight date
and keep in mind, the Vienna Thai embassy wants THREE recent months of bank account documents showing you have at least the equivalent of 20,000 THB (ca 600.- Euro) on your home bank account. While I regard this as being a silly requirement, it is what it is
okay, if you apply 3 or 4 weeks ahead of your flight date, and they issue the METV seven days later, you only lose 2 - 3 weeks of visa validity. Just don't apply 3 months ahead of your planned flight. Why I say 3-4 weeks? Because it leaves time in case they ask for more supporting documents
you can apply for the METV in the E-Visa online system 4 weeks ahead of your planned flight to Thailand. After submitting your application, send an Email to the processing Thai embassy and kindly ask them to issue the visa as close as possible to the flight date you filled into the application, so you don't lose too many days of visa validity. If the embassy staff is attentive and good-hearted, they will make sure to comply with your plea
The Thai embassy and consulates in Germany in the recent years actually took special care to issue a METV as close as possible to the flight date. They do so in order you don’t lose too many days of the visa validity. In Germany, you can apply 5 weeks ahead of your flight, and still get the METV issued only one or two days before your flight date
When applying for the 6-months multi entry Tourist Visa by the E-Visa system, you normally wait until 4 weeks before your planned flight to Thailand, to submit the online application
Many people reported, that they were waiting for their application to get approved, while their flight date approached closer and closer
They actually worried too much
The Thai embassy or consulate in the recent years generally took special care to issue your METV as close as possible to your flight date, in order so you don’t lose too many days of the visa validity.
You can communicate this issue with the Vienna Embassy by Email and kindly ask them to issue the METV as close as possible to the flight date you filled into the online E-Visa application