Regarding chords- breezy has already given a good start that could allow one to work out the chords:
"I play it using the G chord as the tonic
'When I[D7th] was a'
now try and work out the melody and see which chords fit
The G family includes C D D7th Em at least
You may need a capo to fit your voice range"

For those for whom working out chords is a daunting task, you might try the chords listed at the following link: Raymond's Folk Song Page

If I Had a Son (Phil Millichip)
A
When I was a boy, I was ready and willin'
........................................................... E7
To act like a man and to work for me pay
........................... A
So I went underground when the hooter did sound
........... D ...................................... E7
And I worked all me best years away.
A
I've seen men go down there who never returned
.......................................................................................... E7
And I've seen men who lived but had wished they were dead
........................................ A
When the choice is you eat or go hungry
........ D .................................... E7
You see that your children are fed.

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Does any of the above help?