A commuter who received a criminal conviction and a $700 fine after receiving oral sex on the train wants to know 'how can you be so lucky and unlucky in the one day?'

Shane Brennan, from Wollongong, south of Sydney, pleaded guilty to willful and obscene exposure and behaving in an offensive manner in court on Tuesday.

Mr Brennan said he started speaking to the woman - who had a 'mad body' - on the train platform when she said, 'I'm horny, will you f*** me?'

He now regrets his actions that followed after he received a 'bollocking' from a magistrate, his encounter was written up in the regional newspaper and his partner may find out.

The man (pictured) who received a criminal conviction and a $700 fine after receiving oral sex on a train says he would not do it again

The woman was apparently masturbating in an empty train carriage when the encounter occurred (stock image)

'(The woman on the train) was pretty horny and ready to go. Toey as,' Mr Brennan said on Wednesday.

He declined to have sex with her - but when the woman started masturbating on the otherwise 'empty' train carriage they shared he decided he would let her perform oral sex instead.

No one was in the carriage during the late-morning service, he claimed, and the sexual encounter was over in a matter of minutes.

'As soon as the deed was done I was out of there and off,' he said.

But the crime was all captured on train CCTV and staff were waiting on the platform when the train pulled in, the court reportedly heard.

'I didn't know they had cameras all throughout the train,' he said.

The Illawarra Mercury, which first reported the story, said the court heard when staff entered his carriage at Wollongong station they believed he had urinated on the floor.

But the Mercury said he told police it was actually Coke he had poured from a bottle to rinse himself. It was for hygiene reasons, he told the Daily Mail.

'As soon as the deed was done I was out of there and off,' the commuter said

The woman was a bit younger than him, he said, but 'wasn't a good sort'.

It's unclear whether she ever got in trouble for her lewd behaviour, something he finds outrageous.

'She was the one masturbating.

'If she didn't offer me nothing I wouldn't have f***ing done it.'

A man approached a woman who was masturbating on the train, received oral sex from her, before washing his genitals off with Coca-Cola (stock image)

Meantime, the magistrate 'wasn't happy' with him in court this week.

'He said I well and truly crossed the line. And that sort of behaviour can't be tolerated, which is understandable.'

Mr Brennan pointed out there was no one in the carriage at the time and 'you'd think the train guard would've said "good on ya, mate".'

He would not do it again- and has been placed on a 12 month good behaviour bond - but asked: 'How many f***ing men would have knocked it back?'