There are three ways to say "Bangkok" in Thai.
Krungthep is the most common and is used both informally and formally.
Krungthep Mahanakhorn is used in formal settings such as in contracts or people reading the news.
Then Bangkok's "full" name which is never, ever used. It's not ever used when people talk about how long it is and if they can remember it. Even the most formal legal documents won't use it.
Thais often learn the full name at school with a song. A little bit like the alphabet song.
