I have been asked a question which I cannot completely answer so will throw it out to wiser people then I...

Lady born in USA, now in mid 30's, both parents are Thai.

I know that Thais obtain citizenship when born overseas of a Thai mother but is there an age limit? i.e. Does this right expire say at 21 years of age, etc.?

Regards, Bapak

No age limit. If one is born to a Thai parent (mother or fahter) one is Thai.

Edit:

One doesn't lose the right to apply for a Thai passport. She is already Thai, just need to proof that.

It does not expire. She is a Thai citizen.

If she has proof that her parents are Thai she can go the the Thai consulate and get a Thai birth certificate and passport.

It does not expire. She is a Thai citizen.

If she has proof that her parents are Thai she can go the the Thai consulate and get a Thai birth certificate and passport.

Thanks, Guys. It is what I thought but did not want to commit myself...

Cheers, Bapak

I just got back an hour ago from speaking with representatives from the Royal Thai Consulate today about this same issue. My mother is Thai, but she never applied for a Thai birth certificate for me (I only have an American passport and birth certificate). I am now attempting to obtain a Thai passport to prove I am a Thai citizen. They indicated even though I'm 38, there should be no problem. I just need to help my mother renew her Thai passport or Thai ID card, and she should be able to apply for the certificate on my behalf. There is no age limit. Good Luck!

Correct, the help of the parents is necesarry to get all the required documnets to apply for the Thai birth certificate. But it should be a painless process if they cooperate.