Legal Guardian

[ubonrthai]

My wife is a Thai/U.S. citizen and wants to try to get her niece a tourist visa to go to the U.S. for a visit. We raise the child in our home and she is on my wife's tabianbaan. Is that enough to be considered a legal guardian for purposes of applying for a visa or does she need to work on obtaining some other kind of document? The tabianbaan has always been all we need to do any kind of paperwork for her in Thailand so I'm not sure if there's something else we need. If you know the Thai script name of the document that would be helpful. The birth mother legally signed her parental rights to her father around birth so he is the only birth parent in the picture. Thank you.

Edited January 19, 2022 by ubonrthai

[Dogberry]

I've recently posted a similar question here. Not seeing any replies to your question I was wondering  what you were able to find out.