Send a formal complaint to The Ministry of Foreign Affairs of Thailand and ask for a refund and ask them to amend their technology to take this into account..their email of various ministers is on their web site. Quote your DTV case number as reference GL
It does that sometimes, their systems especially regarding payment are clunky to say the least. Check if the payment has gone through your bank account yet.
The only important thing is to keep 500k THB or equivalent as proof of funds, then if you did get asked some questions, just show them the latest bank acc screen short, that really answers any concerns they may haveš¤·š¾āāļø
Do it yourself, read the requirements if itās suitable, choose the consulate/embassy that is convenient for you and apply online, donāt apply unless you meet the most important point..you need to have a min of 500,000THB or in an equivalent personal/savings account GL