i am still stuck in limbo as i am not able to go LOS at this time to be there in person to sort out her PP application and it appears the guardians cant do it.

at what age can she do her own PP ?? 16 ?

i never had a reply from immigration. about 4 weeks now ..

When she becomes an adult (at age 20) she doesn't need anyone to sign.

Starting age 15 she can apply by herself, but still need both parents to sign the paperwork( or the parent who has sole custody if that is the case).

Immigration have nothing to do with passport. MFA handle this. Best speak to the Thai embassy in the country you are in and ask them how you can sign a power of attoerney for issued by them, ideally for passports, which can be sent to the guardians in Thailand.