I read that Thai surrogates should be single or divorced so the bio father will be named as father on the birth certificate. I got that from here:
http://www.familiesthrusurrogacy.com/surrogacy-by-country
I've also read that Gammy's surrogate mother is married. Perhaps the surrogate and her husband are the parents named on the birth certificate.
Where did you see that surrogate is married? As far as I can tell, she hasn't mentioned her husband in any interviews, and I haven't seen any interviews with her husband on how he feels on this matter, so I don't think she is married.