SINGAPORE - A serial stalker did not learn his lesson and continued to harass a woman, less than a year after he was released from prison for a similar offence involving another victim.

He even sent her a letter claiming that a member of her staff - who he had been stalking before his last jail term - was "a satanic liar and a liability to Singapore".

Colin Mak Yew Loong, 45, was sentenced to nine months' jail on Wednesday (Nov 18).

He had pleaded guilty to one charge each of unlawfully stalking a woman and harassing another.

His victims cannot be named due to a gag order to protect their identities.

This is Mak's third conviction for harassment-related offences.

In December 2013, he was sentenced to three years' jail and a fine of $5,000 for various offences, including cyber-stalking American singer Leandra Ramm, whom he had never met.

He had sent her multiple threatening e-mail and voice messages between 2005 and 2011.

The ordeal caused Ms Ramm to develop post-traumatic stress disorder and later write a book about her experience.

In September last year, Mak was sentenced to two months' jail after pleading guilty to unlawfully stalking a Kazakhstani woman. He had harassed her with 278 text messages and 62 e-mails from November 2018 to July 2019.

In the latest case, Mak stalked a foreign national, who is a music teacher here, between October 2018 and 2019.

Court documents state that he prepared and printed at least 20 pages of documents, including pictures of the woman and her musical performances. He left these documents, which also contained allegations that she was working illegally and committing offences in Singapore, at a location where they could be easily found or given to the victim.

Mak also attempted to meet the woman on two occasions - in June and July last year. He failed to encounter her the first time, but spotted her on the second occasion.

When she saw him approaching, she fled into the nearby music school she was working at and hid in one of the classrooms. Mak eventually left the premises without meeting her.

The woman eventually lodged a police report in October last year.

Her victim impact statement, which described the emotional toll his actions had on her, stated that she would cancel potential events for fear that he might show up and harass her.

Mak also sent the general manager at the music school several documents between 2018 and last year, which claimed that the music teacher was working illegally in Singapore. He even turned up at the manager's workplace during that period, saying the same allegations to her.

Mak later wrote a letter to her on July 8 this year, almost 10 months after he was released from prison for his previous conviction.

Among other things, the letter claimed that the music teacher was a "satanic liar" and had moonlighted in violation of her work pass.

It also stated that "things can get very legally complicated" for the director of the music school and the teacher, and that "prosecutions will follow" if they refused to surrender to the Immigration and Checkpoints Authority.

On Wednesday, District Judge Jill Tan noted Mak's mitigation plea, in which he urged the court to give him a lighter sentence as he was a "loyal citizen of Singapore" and wanted to "enforce the law" on the music teacher.

She backdated his jail term to July 16, when he was remanded.

For unlawfully stalking the music teacher, Mak could have been jailed for up to two years, or fined up to $10,000, or both.

He could also have been jailed for up to six months or fined up to $10,000, or both, for his harassment offence.

These are enhanced punishments under the Protection of Harassment Act, which Mak is liable for due to his 2013 conviction.