Heng Li Ying, 29, sold access to the footage via online forums, Channel News Asia reports.
She pleaded guilty to three counts of privacy invasion.
Her lawyer said his client was truly remorseful for her actions for making the videos, which featured women in various stages of undress.
She sold videos to at least 22 people, at a price of either 10 cents (£0.06; $0.07) or 20 cents per second of footage, the Strait Times says.
According to the news site, the gym contacted the police when they were alerted about films of their members circulating online.