Relative clause: Can I put this/that in front of the noun modified by the clause?

[Iwanna]

Usually, 'a/an' and 'the' are used, but I sometimes, though rarely, notice that/this/those/these are used to replace them, such as:

I don't know that guy who is talking with John over there.
...except those things which constitute the bulk of our exports and cannot be protected.

Is that the right way we use a relative clause?

thanks

[Skrej]

Both your examples are perfectly acceptable.
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[Iwanna]

Thank you, Skrej.