About Lady Boys (Katoeys)
Anyone visiting the nightlife scene in Bangkok and around Thailand most likely is familiar with the presense of many (relatively speaking) lady boys or katoeys (in Thai language).
I think the generally accepted term for this third sex is transvestites. Most of them in daily live have upgraded themselves with female attributes like hairdo, prominent breasts, fancy dresses, a lot of make-up etc. In Thailand there is also a well established prevalence of gender surgery where the male sex organs are removed and remodeled through plastic surgery into female sex organs.

The above surgery is performed rather frequently. One supposed reason being that there is less importance given to psychological evaluation before surgery as done in the West. The prove that some of these persons have psychological problems is clearly found in the fact that a lot of them end up in the sex trade, rather than leading an otherwise normal life.

There used to be a time when most of the larger bars at Nana Plaza (and some at Soi Cowboy) had a contingent of lady boys. Possibly they were kind of liked by management because they were rather agressive in promoting themselves with the customers, thus generating income for the bars. On the other hand, they were more likely to generate trouble in and out of the bars. Some customers probably got more than they bargained for, when seeing their 'lady' emerge from the bathroom in the hotel. So nowadays lady boys have mostly disappeared from the regular a-go-go bars.

The main problem with lady boys in the bars was deception. While some customers may prefer their presence and services, a lot of first time visitors somehow fail to distinguish between them and 'normal' women. And the lady boy will certainly not tell them what they are.

But for those who prefer their services, the three floors at Nana Plaza have bars that solely have katoeys working in them. The longest established bar is Casanova on the second floor. At present also Obsession on the ground floor, and Cascade on the third floor, have lady boys in abundance.

Many lady boys are working the streets around Nana Plaza. Quite a few position themselves at the entrance to Nana Plaza itself, looking mainly for drunk males, about to leave Nana Plaza without a companion yet. In the evening and at night, the Sukhumvit section between Soi 3 and Soi 5 ( Foodland) has besides a lot of street prostitutes, also a big bunch of lady boys working the field.

At Soi Cowboy, lady boys are less prevalent. However, there are a few of them working at the Soi 23 end of the soi. If you leave Soi Cowboy from that corner alone, you should not be surprised when followed, touched, by lady boys, wanting your attention.

How to recognize lady boys or katoeys. The answer : It is like distinguished between men and women, or between cats and dogs. You know what is a cat or a dog, when you see it, without needing to go over their different body parts before making a decision.
It is a given that MANY male customers visiting the nightlife scene lack an ability to figure out the katoeys though. Long-time residents usually can recognize them from a distance. (But one should never assume one is a total expert, since some lady boys are well 'done' indeed)
Most strictly speaking 'male' attributes can be corrected nowadays by surgery. Breast, sexual organs, buttocks shape, Adam's apple can all by adapted, removed or added. General physical appearance usually is more difficult to change. Big muscles, wide shoulders, large hands and feet can give a good hint.
Besides physical characteristics, general behaviour of katoeys can be a give away. It can be summarized as : They try to hard to look and behave like females. Their body movement are frequently exagerated. On the other hand, if you have an argument with them, you will see the 'male' part get out of its cocoon.

As an added precaution : Most of the katoeys working the streets do so in groups. So while you may be talked to by one person, more are observing you all around, and may try to join the action. The katoeys close to Nana Plaza reportedly also have been known to be good pickpockets.