"Everyone was yelling at him and he slowly became aware that he was being uncouth. He pulled up ... and wobbled back to the other end of the plane."
The man and a friend were seen drinking whisky before take-off.
"Him and the mate were sitting there and mixing it in Burger King cups. Six hours later they were catatonic," Mr Chapple said.
The man left the plane with only a warning and Singapore police were not called to deal with the matter on landing, he said.
Jetstar crew gave wipes to the man who was sprayed and moved him to another seat, but Mr Chapple was left sitting next to a large reminder for the rest of the flight.
"We were sitting next to a pool of urine for a good five and a half hours. You couldn't see a puddle but you could tell it was there. It was pretty outrageous."
The female passenger whose scarf was sprayed had to repeatedly ask for a plastic bag for the soaked item, said Mr Chapple.
Mr Chapple criticised the way the Jetstar crew handled the incident, saying they were "slack".
He said he confronted the man in Singapore and asked him "what was that all about" but the man did not know what he was talking about.
"I told him that he had pissed everywhere and he looked quite shocked," Mr Chapple said.
JetStar said the urinator was issued an official warning from the plane's captain, had his alcohol confiscated, and returned to his seat to sleep off the public incident.
Jetstar last night confirmed that "there was an inebriated passenger who engaged in inappropriate and disruptive behaviour", but maintained police did not need to get involved.
"We issued our final warning ... if you don't behave after the warning, then it becomes a matter for federal police," said airline spokeswoman Jennifer Timm.
Jetstar was contacting the customers affected by the incident to arrange compensation.
They would probably get a $200 voucher and an apology letter.
INFLIGHT HORRORS
August 27, 1989: Izzy Stradlin of Guns N' Roses arrested at the Phoenix airport after urinating on the floor of the plane, apparently upset at having to wait for the bathroom.
April 21, 2001: REM lead guitarist Peter Buck cleared in court after a drunken rampage aboard a British Airways plane, where, among other things, he allegedly sprayed flight attendants with a pot of yoghurt.
December 3, 2003: A Canadian man, 39, became drunk on a Cathay Pacific Airways flight from Hong Kong to Melbourne. "He then punched a flight attendant in the stomach, threw his shirt at a flight attendant's face and urinated in the aisle and against the toilet door," said a state prosecutor.
June 2, 2011: Rats were found aboard a Qantas flight from Sydney to Brisbane shortly before takeoff. A spokesman for Qantas said it was "a very irregular occurrence".
