How can Americans in Thailand get their birth certificates notarized?

unfortunately your question doesn't sound in the least like a thai VISA question.

Sadly (for you) the group has a very narrow focus and is about questions for visas to thailand.

To get your answer IF you're in Thailand you go to the American Citizen Services website and read about how to get things notarized.

Because birth certificates are issued in the US by individual states you can't get the birth certificate itself notarized. What you do is a "blank notary" and fill out that "document xxxx, a birth certificate issued in xxx on xxx is a real and true document". <- Then they notarize your signature on that document.

Good Luck (y)

Well Comrade...

What do you need it for?

Teaching license or Non B?

Do you have your birth certificate with you now in Thailand?

The US Embassy can notarize documents in Bangkok and Chiang Mai for a fee...and appointment needed.

A Thai Lawyer may be able to Notarize...if allowed by receiving agency where you are submitting it.