Faced with marital problems, he wanted to get back at his wife, a tutor. So the assistant manager decided to target her pupils, who were at their home for lessons.
The 44-year-old man hid a recording device in the toilet and recorded a video of two 11-year-old girls, who are twins, when they went to use it.
The man, who cannot be named to protect his victims' identities, was jailed for 10 weeks yesterday after he pleaded guilty to one charge of insulting the modesty of one of the girls.
A second count for a similar offence involving her sister was taken into consideration during sentencing.
The siblings were at their tutor's home at around 4.30pm on Sept 27, 2015.
Before the class started, both girls went to the toilet separately. One of them spotted a recording device partially hidden in a basket on the right side of the toilet bowl. The device was in a black pouch with the lens protruding through a hole.
The girl then told the man's 35-year-old wife.
Deputy Public Prosecutor Ho Lian-Yi said: "(The wife) retrieved the object from the kitchen toilet and realised that the object was a recording device... (She) privately confronted the accused and handed the object to him, hoping that he would confess and apologise. However, he vehemently denied what he had done."
He later told his wife and the girls that the object was a thumb drive which he had left behind.
The twins accepted his explanation and did not tell their parents about the incident.
DPP Ho said: "(The wife) did not inform the police about her discovery at first. However, after she discovered broken links in the accused's Internet (browsing) history for titles such as 'G-String' and 'Upskirt', she convinced him to move out of their house." This was on May 10 last year.
She informed the police five days later. The man surrendered to the authorities the next day and came clean to the officers about his offences.
For insulting the girls' modesty, he could have been jailed up to a year and fined.