The multi-millionaire singer stunned staff at Ladbrokes in her home town of Blackburn, West Lothian, by inquiring about the £6-an-hour post in January.
The 52-year-old said her career was going through a quiet period at the time.
She said her upbringing meant she still worried about her finances, despite her estimated £11 million fortune.
She said: "It's a kind of habit I can't get out of, to do with my working-class background. I never really had a lot of money.
"It's a kind of habit I can't get out of, to do with my working-class background. I never really had a lot of money.
"I just went in on the off-chance. It was kind of a desire to be normal. And it was a quiet period. I just got panicky."
"But I wouldn't want to scrap the job I already have. I absolutely love it."
She saw an advert for the job while walking by the bookmakers, and went in and spoke to deputy manager David Corr, 28. He told Susan she would have to apply for the role online at the Ladbrokes website.
Susan is about to embark on a 19-date UK tour, her first since shooting to fame on Britain's Got Talent in 2009