Two days after he was given probation for taking upskirt photographs, Clemence Koh Junxiang was back to his old tricks.

The 18-year-old, then a second-year Ngee Ann Polytechnic student, was found to have 2,744 "voyeuristic pictures'' of "100 to 150'' women on his Apple iPhone, taken after he trespassed into the school's female toilet and at other locations around the island.

Yesterday, he pleaded guilty to 10 of 140 charges before Community Court Judge Lim Keng Yeow who, in July last year, had given him a chance by placing him on 24 months' split probation.

Last June, Koh was convicted of six counts of insulting the modesty of a woman and had 56 other similar counts taken into consideration.

One of the probation order was that he was to use only a cellphone without camera functions but he breached that by getting a camera phone from a friend and kept it away from his family.

Deputy Public Prosecutor Tan Ee Kuan said Koh was caught after a 17-year-old student reported him after noticing a mobile phone in a toilet last August.

She waited for him to come out of the cubicle where he was hiding. When he did not, she told her classmates and the school authorities. A security officer then detained Koh.

Investigations showed that he had trespassed into the toilet and locked himself in a cubicle.

Over the next two hours, he took a total of 184 photos of seven females who used the neighbouring cubicles.

He also took an upskirt photo of a schoolgirl on an MRT train and an unknown woman at Daiso in Plaza Singapura.

He trespassed into a female toilet at the Singapore Institute of Management headquarters and took a photograph of a woman's exposed legs at a neighbouring cubicle.

He was remanded pending progress and reformative training reports on Feb 11.