I read a short story recently that said :

Chaith mé an Satharn ag an abhainn, agus bhí an-lá agam. Chuaigh mé ag marú breac.

The question being on

Chaith and Chuaigh

First in the Ulster dialect would the sound more like :

Khy - khwee

and wouldn't it be ending in a inn/ainn if conjugated as happening? ex: labhraíonn

Go raibh míle maith agaibh a chairde :-) Is maith liom sibh ^_^

First in the Ulster dialect would the sound more like :

Khy - khwee

No, not really.

and wouldn't it be ending in a inn/ainn if conjugated as happening

No, that's a different tense altogether.

Oh, by the way.

My answer No, not really is far from perfect, of course I'd like to tell you the correct pronunciation. Do you IPA?

In Ulster, they tend to pronounce "ch" as a "h", eg:

Chuaigh : Huaigh
Chaith : Haith

In some cases they do, but at the beginning of the word it is much more common to pronounce it as "ch" [x]. For chuaigh and chaith both Ó Baoill and Ó Siadhail give [x]

I don't know IPA, just a slight idea in English spelling will give me the idea. How would it be a different tense?

It would be a different tense because:
labhraíonn is in the present tense, it denotes an action taking place now or a continouos action that hasn't ended.

labhraíonn sé = he speaks

Both chuaigh and chaith are in the past tense, an action which has taken place and is completed.

chuaigh sé = he went
chaith sé = he spent

What about "Cuaighann sé" As in he goes...or Caithinn sé....he spends

Can Caith be used in the sense of money too?

"Chaith mé trí leathphunt sa siopa aréir"

Caith is a multifunction verb

Chaith mé cloch - I cast a stone
Chaith mé toitín - I smoked a cigarette
Chaith mé bliain thar lear - I spent a year abroad
Chaith mé punt aréir - I spent a pound last night

Chuaigh sé - he went
Théadh sé - he used to go
Téann sé - he goes.

téigh is the verb, and it is irregular.

The verb to go is irregular in almost all languages, at least almost all Indo-European. Think of English "go" - "went", German "gehen" - "gegangen" or Welsh "mynd" - "aeth". Irish is no exception to this general tendency.

Chuaigh sé = He went
Téann sé = He goes
Rachaidh sé = He will go

Also, you cannot say "Caithinn sé", you mean "Caitheann sé".

And finally, yes. Caith can be used both about spending time and about spending money.

Caith = throw/spend/wear

In Gaeilge, you "spend" a cigarette.
Chaith sé toitín.

He wore a jumper.
Chaith sé geansaí.

Also, here comes the idiom of all idioms:

Caithfidh mé imeacht.
I have to go.

Caithfear an obair a dhéanamh.
The work has to be done.

Is ea, caith is a most useful word. May I add that Chaith sé geansaí to me at least has an idea of wearing it out. If I'm just saying he wears a jumper today I'd go for Tá geansaí air but the meaning that Fear na mBróg brought forward is of course also correct.

Just to further complicate matters: In Munster, caith - lika all other verbs - is of course conjugated for each person. To say I have to go I always say Caithfead imeacht.