Can I have a sponsor for the 500k requirement for a Thai visa?

Sponsor letters are usually for main applicant (parent, spouse) who are applying for a DTV for their dependants (immediate families). Your best bet is to borrow the 500k and have it in your bank account with your name. A lot of people were able to use their bank statement with the money transfered within days of application.

However, if you search this group, someone recently was approved with a sponsor letter from their family. I can't remember which embassy approved this but it's a first I've heard. So maybe try a different country if that's possible for you

Your best course of action is to have your sponsor bank the cash into your bank account, but even then, you might have to wait until it has been in your account for three to six months. It is ridiculous that each embassy can make up their own rules, but that's the system that we have to live with. Good luck.

Each embassy has the final say, so if they are telling you this, then it is possible. From what I have seen, sponsorship option has not worked, unless it is your employer.