OK - without the tune, but I've given it a go. The problem is that it is vernacular poetry and needs something other than direct translation. There's one bit that I can't do properly ... although I could ask around. I've put in a 'filler' for now. I've also tried to call on the 'commonalities' you get in Welsh folk song for some phrases - thought they sounded more natural.

Cloudy in the East & it looks like rain,
Looks like rain boys, looks like rain
Cloudy in the east & it looks like rain
I'm on my long journey home.

Cymylau ar y gorwel, mae'n bygwth glaw
Bygwth glaw, bois, bygwth glaw.
Mae siwrnai hir o'm mlaen.

(Literally, clouds on the horizon and it threatens rain, threatens rain, threatens rain. I've a long journey ahead of me.)

Lost all my money but a two dollar bill (repeat)

Wedi bradu fy mhres i gyd ond un papur punt
Un papur punt, bois, un papur punt

(this is the one I had trouble with because of the American saying "As phony as a two dollar bill" so there's an added texture in the English. I don't know what the British equivalent would be. Anyway, I've put, "Wasted all my 'brass' but for a one pound note". It probably should have something to do with shillings, etc.)

White smoke rising:
Mwg gwyn yn codi, oes sôn am trên?
Sôn am trên, bois, Sôn am trên.

(Lit: white smoke rising, any hint of a train?)

Black smoke rising:
Mwg du yn codi, oes sôn am trên …

(as above)

Homesick and lonesome, feeling kind of blue:
Hiraeth yn fy nghalon, dan felan ddu,
Melan ddu, melan ddu…

(Lit: hiraeth in my heart, 'under' a black melancholy. "Y felan ddu" is the Welsh phrase for 'the blues'.)

Hope that's some help. You must call in at Ty Gwerin when you're at the Eisteddfod and have a cuppa!

siân