An Indonesian maid terrorised her employer's bedridden husband by threatening to kill him if he did not reveal his ATM personal identification number (PIN).

Eko Alviah, 30, who placed a pair of scissors at the neck of Mr Chew Seng Mun, also threatened to cut his nipple on Sept 23 last year.

After the 60-year-old had given her a false PIN out of fear, she bound and gagged him with duct tape to prevent him from seeking help, as she knew that he could still shout and move around slowly. She also locked the bedroom door.

She forced open a locked drawer in the master bedroom to look for her passport.

She found a box with 25 pieces of jewellery worth a total of $2,648. She then fled from the Woodlands flat with her passport and the jewellery.

She also stole $100 that was on the living room table before leaving the flat. She had been working for the household for about a year at the time.

Her main duty was to take care of Mr Chew, who had Parkinson's disease and has since died.

Deputy Public Prosecutor Jaime Pang said Eko went to Woodlands North Plaza and tried to withdraw money using Mr Chew's ATM card.

When she could not withdraw any cash, she threw the card away.

At about 11am, she boarded a ferry for Batam, Indonesia, where she sold the stolen jewellery to a makeshift stall for about $140.

Meanwhile, Mr Chew's son found his father taped and bound after unlocking the bedroom door with a spare key.

DPP Pang said Eko remained in Indonesia for the next seven months.

In February this year, she enrolled herself at several Indonesian maid agencies, but was found to be medically unfit to work in Singapore.

Two months later, she applied for a new passport and made private arrangements to work for an employer here as a maid.

On May 9, she was screened at immigration when she tried to return here and was arrested.

Investigations further revealed that Eko had stolen $700 from Mr Chew's wallet some time in December 2015 while he was sleeping.

She spent the money on a mobile phone and other personal items.

Yesterday, Eko pleaded guilty to three charges and was sentenced to 50 months in jail, plus another 12 weeks in jail in lieu of caning.

DPP Pang cited numerous aggravating factors when he sought a jail term of at least four years to be imposed.

District Judge Chay Yuen Fatt, who took four other charges into consideration, said he had considered in particular that Eko had preyed on someone she was supposed to care for.

"She took advantage of his age, of his disability and of his vulnerability in order to commit the offences, which were highly selfish and mercenary."

The robbery offence carries a mandatory minimum of six strokes of the cane on top of a jail sentence of up to 10 years.

But women, as well as men above 50, cannot be caned.

The judge backdated her sentence to May 11.

She could have been sentenced to seven years or more for criminal intimidation, and up to seven years and/or a fine for theft as a servant.