If a guy ask if you're married does that mean he's interested?

Not necessarily, It could mean he is interested, but it could be in a different way then you would like. It could mean he just wants to get in your pants. But it also could mean that he may be interested. Most likely he just wants go get in your pants. But that's just my opinion.

In some countries (Asia), it is just a polite question to ask other people. Otherwise, I agree with above

He may just be curious. I would look out for more hints, before jumping to conclusions.