How to tell if your Thai girlfriend is already married

From Asian Sweetheart"...I look at her ID card and it's obvious she was married before. That's because the title before her name is nang which means "Mrs." If she had never been married it would be nang sao which means "Miss". The title of nang is kept even if the lady gets divorced and reverts to her maiden name. Then I look at some of the letters the couple wrote to each other, letters they will use to prove the existence of a long term relationship. And in the letters the lady says she was never married."