For example, in Indonesia we have "rakyat". In English we may have citizen but the word actually has power connotation rather than powerless connotation.
Another word is peasant. But that seems to mean those living in village rather than the lowest ranking people in society.
Here, when I say lowest rank, I mean lowest rank in political power. Most of us, for example, are just "people" no matter how rich we are.
So what's the word for the lowest rank member in English?
You might consider using the word peon. I believe that it has the meaning you seek; additionally, it also carries the connotation you're looking for. Finally, it's informal enough to be understood in everyday speech.
The word pleb can be used to describe very lowly people in political terms.
Western society does not have explicit castes, and even notional/nominal class is tied now more to education and profession than to birth. In fact, it is more than a little bit politically incorrect to talk about these things, because it condemns people for things beyond their own control.
If you are talking about somebody who’s nobody special, you might try for an average Joe or Joe Everyman. This is a bit less unkind than calling a member of the masses a “nobody”.
Moving into strictly pejorative territory now, per the OED, a lowlife (irregular plural lowlifes instead of *lowlives) is “a coarse, vulgar, or no-good person.” Inspecting a thesaurus will lead to countless synonyms of such good-for-nothings and scoundrels.
Similar queries can be constructed if you are more interested in focusing on them as uneducated and uncultured know-nothings on the one hand, or on the other, as the poor unfortunates and related do-nothings who make up the unproductive non-working class, sometimes called the permanent underclass. In earlier times, and perhaps even now, these unscrupulous cads were also called stick-at-nothing, for which the OED gives the example of “a false, lying, swindling, underhand, stick-at-nothing brute.”
If there is any connection to be found here amongst these many pejoratives, it is the “nothingness” link connecting good-for-nothing, do-nothing, know-nothing, and stick-at-nothing.
The lowest-ranking person in society might be a serf:-
a person in a condition of servitude, required to render services to a lord, commonly attached to the lord's land and transferred with it from one owner to another.
or perhaps a churl:-
a. A ceorl. b. A medieval English peasant.
Slightly higher in the pecking order would be a villein:-
One of a class of feudal serfs who held the legal status of freemen in their dealings with all people except their lord.
The precise gradations and the names used would depend on which part of the world we are discussing, and the historical time. In modern times, the lowest of the low would probably be a chav:-
a young lower-class person typified by brash and loutish behaviour
Moving over to India, we might find an untouchable:-
Hinduism. the former name given to a member of a lower caste in India whose touch was believed to defile a high-caste Hindu; Harijan.
There are many words to describe the lowest class of society. The ones that haven't been mention yet are: Underclass and Working poor.
What about 'dregs of society'?
'pleb' and 'serf' are good approximations.
For a term that is not archaic, is neither pejorative nor exalting, how about 'hoi-polloi'?
Not so much, in terms of "rank", but another useful term that I can think of is "Social Pariah" from:
http://dictionary.reference.com/browse/pariah
noun
1. an outcast.
2. any person or animal that is generally despised or avoided.
3. (initial capital letter) a member of a low caste in southern India and Burma.
It's sometimes used colloquially as:
"No-one ever asked Tom for a beer, he was the social pariah in the office."
In a society without a rank structure, it's hard to come up with a word for the lowest rank.
However, there is this idiom: cog in the machine.
The phrase is used to describe an insignifcant or unimportant person, often made to feel dehumanized. One website explains how the expression refers to "an unimportant part of a large enterprise; an exchangeable piece of equipment" that's "used in a very negative sense when expressing dissatisfaction with one's position." Dictionary.com defines it as: One who holds a minor but necessary post in a large organization.
An ordinary person, without rank or title.
Use mudsill. Here are the references: link1, link2
Use heel, but I suspect it's really rare. link3
Use plebeian. link4
Nonperson comes to mind, although it is supposed to mean someone who is so low that they actually fall out of society altogether.
In some (but apparently not all) Western countries, we think everyone is equal. But in fact there are people with less political rank than citizens. They are called prisoners. Prisoners often do not have the right to vote or participate in juries. The civil liberties (freedom of speech, association, privacy, etc.) of prisoners are often more limited than those enjoyed by citizens.
"I know my place."bbc.co.uk/programmes/p00hhrwl