Canvas-maker Alvin Yeo Pei Jin, 49, called himself "Happy Tan" on Facebook, and instead of his own picture, used that of an unknown, good-looking Taiwanese man.

He did this to woo women, but he was on the prowl for a specific target - middle-aged women with long hair. Once he found someone he liked, he added them as friends and initiated a chat. It did not take long before the chats moved on to phone messaging, and he would ask the women for their nude pictures.

Once he had the nude photos, Yeo threatened to expose the women, unless they had sex with him.

For his actions, Yeo was jailed for 13 months yesterday, after pleading guilty to five charges, including mischief, and insulting the modesty of a woman by filming a colleague in the shower in 2009. Ten other charges were considered during sentencing.

The first victim, aged 52, accepted his "friend request" in April 2015, and met him twice for dinner.

Around July that year, he started harassing her to meet for sex. When she kept refusing to do so, he threatened to post nude photographs of her that she had sent him.

She deleted her Facebook Messenger out of fear, and reported him to the police on July 13 that year.

The second victim, aged 48, was someone his family knew. He found this out after he asked her for photos and she sent him pictures of herself.

During their chats, he told her he was a widower with two children, and that he lived in Redhill. He asked her for nude pictures and she sent them to him over the next few days, in the middle of last year.

Yeo wanted to have sex with her after he got the photos but hesitated because he looked different from his Facebook profile picture. So, he devised a plan to force the victim to find five men to have sex with, hoping he would be one of them.

On June 14 and June 15 last year, he sent multiple WhatsApp messages to harass her. Among other things, he threatened to show the nude pictures to other people, including her friends and relatives, if she blocked him on Facebook. He also threatened to leave her nude pictures outside her home so her husband would see them.

The victim was shocked, as she had not revealed any of her personal details to him. She blocked him on Facebook and WhatsApp, and made a police report on June 15 last year. Four days later, she made another police report when she found an A4-sized full frontal nude picture of herself, but with her face torn off. It was stuck on the gas meter outside her home.

Yeo also left messages for her on the gas meter. One said: "Tomorrow, if you don't reply to my message, I will post your big face at the door there." On June 21, he used a black marker pen to write "Block me, waiting for death" on the wall outside her home.

Yeo's lawyer James Ow Yong said his client's wife is suffering from degenerative diseases, and has been using a wheelchair for about four years. They have two children.