Can you be a bit clearer on this. You say the Embassy won't approve your visa with a sponsor guarantee for 500k. Then you say you approached a visa agent who told you, you'd have to do it again in three months? Do what? Also you say your visa was approved if this wasn't from you applying in the first instance, was it the visa agent applying for you and if so, why would you have to apply again in three months and apply for what? Hope these questions make sense.
It's relatively new, so nobody knows until they confirm on FB. Take things people on FB say with a pinch of salt. The ones giving spurious advice more than likely are not even on the DTV visa.
It doesn't say whether it has to be a current account or a savings account. All they want to see is that you have either 500k THB in a Thai bank account or equivalent in a foreign bank account.
All anyone has to do is inform their bank that they're going abroad, including days you'll be out of your home country and tell them which country/s your going too. This applies, well in my case to transferring money.
I transferred money through Wise December 2023,from my UK bank account, to a Thai bank account that is a Thais account. I used my banking app., with Surfshark and no problem.