What papers to exit Bangkok with my Thai-Australian 12yo

[lolex]

What documents do I need to fly out of Bangkok with my 12 year old Thai-Australian daughter.

 

She has both Thai and Australian passports. She travelled to Australia once before exiting Thailand on her Thai passport. Her Australian passport was issued in Bangkok but that is not recorded on the page with her picture ...it just says issued Australia. There are no stamps of any kind in her Australian passport.

Her last name is the same as mine in both passports and her ID Card.

 

I've read somewhere ages ago that a document from her mother issued at the Amphur is needed. I also heard that a letter from her Mum stamped at the police station works. And finally I've heard that because we share the same surname there should be no problem.

I don't like to take risks.... especially because missing flights is very expensive.

 

Good  advice (like... been there, done that advice) will be very much appreciated.

 

Thanks a lot... Marko