If you've spent much time in Thailand you will quickly realize that virtually everyone has a nickname, which they use exclusively instead of the name that is listed on their birth certificate. Even in formal settings such as the workplace, you will find many Thai people going by their nicknames.
The practice of using nicknames in Thailand is a cultural tradition which dates back to the Sukhothai era, where babies were commonly named according to their birth order. Nicknames evolved into describing a baby's appearance, for example, short, long, thin, fat, dark skinned or light skinned.
The use of nicknames in Thailand was also seen as a defense from malevolent spirits who might want to steal a baby or interfere with its life. It was thought that using two names would help to ward off these spirits. Giving a child an undesirable name, such as "pig", "fat" or "dog", was also believed to discourage nefarious spirits from wanting the child.
By 1919 Thai law required the use of surnames, mainly for identification purposes. Curiously, no two families in Thailand are allowed to share the same surname. This means that any two people with the same surname must be related in some way.
In modern times, some Thais believe that using nicknames makes them harder to track by the authorities or people looking to cause them harm. In some ways this is true, private investigators do need to uncover a person's real name in order to track them through paperwork, as nicknames are not recorded officially... At least not at the time of writing.