A jobless man pretended to be a doctor and handed out free pills to women in the Jurong Polyclinic. Oh Koon Shin, 52, who handed them sleeping pills, then stole from them after they became drowsy.

In a district court on Friday, he pleaded guilty to administering a stupefying drug with the intention of committing theft. He will be sentenced on April 1.

On Dec 28 last year, Oh got Madam Koh Jew Tiang, 82, drowsy in the clinic and stole her necklace valued at $1,400.

The next morning, he returned to the clinic at Jurong East Avenue 1 and approached Madam Ching Sui Nai. The 62-year-old retiree was feeling ill and he convinced her that he was a specialist and got her to swallow four diazepam pills.

After seeing the clinic's doctor, she was queuing for her medicine when Oh offered to pay and collect it on her behalf. He also got her to swallow four more diazepam pills.

Clinic staff members who knew about the theft of the necklace a day earlier thought that Oh matched Madam Koh's description of the thief.

One of them called police while others kept an eye on him. He was seen rummaging through her handbag and later pulling a ring off Madam Ching. He was detained by staff members and later arrested by police.

The court heard that the sleeping pills were described for Oh as he has insomnia.