Is it permitted to ask questions of female sex workers in Thailand to be familiar with their real life as a tourist?

Thailand is generally a free country and, outside of talking negatively of the king, you are free to talk to anyone about pretty much anything.

This includes sex workers who are people too. While you and others may treat them as another tourist attraction, you can get to talk to them quite easily if you treat them like you would anyone else. People from Thailand are generally extremely friendly and talkative. They are often just as curious about you as you are about them.

The best advice if you want to approach a sex worker is to find where they are many of them and start talking when they are not busy. The truth is that there are so many of them in some areas that you will see dozens waiting a street corners just chatting with each other. They approach males mostly, so as a female you may have to get the conversation started. Just smile and talk to one who is not busy. Try not to make it sound like an interview and be polite.

There are many shades of sex workers in Thailand and you may find that what constitutes one does not coincide with how things are in other places.

As a male traveling alone in Thailand, whenever I'm in a bar, I'm approached by bar-girls hustling drinks. I don't like to send them away since every baht they don't earn from drinks is one they have to earn on their backs.

I usually buy the girl a "lady-drink", 30 or 40 baht for a shot of apple juice with just enough tequila in it to make it smell like liquor, and chat with her for a while. We usually end up talking about her kids -- every bar-girl I have ever met has at least one adorable moppet at home, usually two, and a phone full of pictures of them.

As for "permitted", I've never tried asking them about their work, but since they are fairly enthusiastically asking me to have sex with them, I don't think inquiries into their profession would be taken amiss.

In fact, one time, two bar-girls were working me (at a place that charged an unheard-of 100 baht a drink!) but after an hour hadn't propositioned me. I finally asked them if they were prostitutes. Once I explained what the word meant, they said they weren't -- they were "coyote girls", just dancers and drink-hustlers, but not hookers, a new phenomenon as far as I know -- but they didn't take the slightest offense and offered to find a prostitute for me (I declined).

I'm curious whether as a female alone, you would be approached, but I'm quite certain that if you offered to buy a bar-girl a drink, she'd be more than happy to talk to you. Or sleep with you, for that matter.