Travel Guide for Stateless People

Just to use one example I'm familiar with, by some estimates there are as many as 600,000 stateless people living in Thailand. There are lots of reasons but war refugees are a big chunk; hill tribe people who the government has been unwilling to issue citizenship to for generations are a big chunk.

There is reform under discussion to grant PR and/or citizenship to a majority of them - https://thailand.un.org/en/285279-unhcr-supports-thailand-ma...

Entire families live and die stateless. Alien travel documents exist in some circumstances (as referenced by this guide) but are a very obscure thing, hard to obtain and the process may be arbitrary, airline staff and border immigration officers are frequently not familiar with them, etc.

This is usually not a status that anyone holds voluntarily; they are displaced at some point and the government which controls the territory they are displaced into does not want to enfranchise them, or even their descendants.

All told globally there are 4-5 million stateless people.