Also be aware that, if the date that you plan to travel to Thailand is too far ahead, it is common that embassies put applications "on hold" and approve/issue the visa closer to the intended travel date.
The Thai Embassies and Consulates around the world have various requirements. For the most accurate answer it is best to check the requirements of THE embassy or consulate that you will apply through.
That being said, I did some research (see below) and I would say that your bank statement need to show that your CURRENT balance is above the required amount.
This is how I came to that conclusion:
I searched for info in another fb-group (Destination Thailand Visa - DTV).
According to other people, applying in Germany they approve DTV, even if the money have been in your account for less than 3 month.
I found posts from 2 people applying through the Thai Consulate in Frankfurt and 1 that applied through the Consulate in Munich. I also found some info regarding the Thai Embassy in Berlin.
One applicant (Frankfurt) submitted 3 month of bank statements. Last statement showed a balance of ~ 17.000 €uro. He had transferred 15.000 €uro from his investment account around 10 days before applying.
Another applicant (Frankfurt) wrote that he submitted: "500k baht bank statement (money was transferred just before the application, no necessitity for proof of 6 month in the account)".
A third applicant (Munich) wrote: "Bank statement (pdf) showing only final balance of above 500.000 baht and date".
I also read a post from someone planning to apply in Germany that asked: "Will it be enough if I show them only one month of 500.000 baht in my bank account?"
In the comments a person wrote: "I sent an e-mail to the Embassy in Berlin and they told me one current bank statement is enough."
well I have never used an agent so I have none to recommend. I think, if you write where in Thailand you are, you are more likely to get useful suggestions of agents and their prices.
no you got it wrong... His friend WANTS to do an extension, but is "terrified" to do so because of the problem he had on his entry and that the airport immigration officer said she would make a note in his file.