I looked up "bum" on Thesaurus.com and found these synonyms:
bindle, black sheep, derelict, drifter, floater, gutterpup, guttersnipe, hobo, stiff, tramp, transient, vagabond, vagrant
If you click on some of the synonyms for "bum" or its synonyms you find words like:
beggar, castaway, dawdler, grifter, ne'er-do-well, outcast, renegade, stiff, stumblebum, itinerant, nomad, rolling stone, transient, down-and-out, hitchhiker, homeless person, loafer, panhandler, wanderer, fugitive, gypsy, rascal, persona non grata, itinerant, exile, fugitive, refugee, reprobate, untouchable, wretch, undesirable
In the notes for "bum" it says "a hobo is a migratory worker who likes to travel, a tramp travels without working, and a bum does not travel or work."
Similarly, in the notes for "vagabond" it says "a vagabond refers to a person who leads a carefree, roaming existence; a vagrant ekes out a living by begging and is often considered a nuisance."
So I guess from society's perspective, it's better to be a hobo than a tramp, better to be a tramp than a bum. And it's better to be a vagabond than a vagrant.
Now I'm going to add a word to the list. If you look up synonyms for "exile," you will find that it is treated like a condition rather than a person. In that list is "diaspora," which means "spreading out of a group of people." It's often used to describe situations where the group that spread out was more or less forced to do so, like the Irish coming to America to escape the potato famine (personal connection there).
Here's my word (I didn't coin it) for the list:
Here's my definition (I did create it - Google shows no definitions on-line):
a person who is part of a group that society marginalizes
So, my fellow diasporadoes, now you have a pretty exhaustive list of synonyms for "bum" that you can use in your next beat novel.