How Do I bring a fiance to the U.S. from Cambodia?  I want to know all
of the forms required.  I know I have to file a application for visa
I-129 form and also a G-325. Do I also need an I-134?  What other
applicable forms apply? Do I also have to File 4 copies of the I-134 and G-325?

That is I-129F (and not I-129).
You don't need the I-134. If your fiance doesn't have enought
resources (less than $8,000 and no job waiting for him in the US), you
will need to give the I-134 for his interview at the consulate. An
I-134 is always a plus but only for the interview at the consulate. So
file one and send it to him.

For the filing part (now), I would also recommend you to show that
you're a guenuine couple. So, include letter you sent each other or
photos