Some colloquial usage substitutes them for those. It's not considered proper grammar, but is popular in certain (typically, rural) areas. I would say that your examples come from fiction, and are intended to convey a rustic speaker.
These words aren't there for emphasis (you'll notice that I'm not using "these" in this sentence for emphasis either); rather they are intended to convey that the noun that they're paired with is a specific example, or are specific examples, of the noun. This and these, that and those are demonstrative pronouns, used to indicate some sort of proximity or relationship to the speaker. This is singular and these is plural, and mean a "proximal" or close relationship. That is singular and those is plural, and mean a "distal" or more distant relationship. The proximity involved is roughly equivalent to "here" and "there", and some colloquial usage will say "this here thing" and "that there thing" to emphasize this difference.
These sentences should clarify the differences:
Do you want this sandwich or that one?
In this sentence, the speaker might point at a sandwich right next to him first and then at one further away, not immediately in reach.
These marbles are bigger than those.
In this case, the speaker might be first referencing some marbles in his hand, and then point at another group of marbles further away.
