Madam Chew Siew Leng has a bit of a space problem in her two-storey terraced house - hongbao have taken over every nook and cranny.

Crammed boxes of packets are stacked on couches and chairs, cabinets and shelving units, each meticulously labelled with categories such as "cosmetics", "insurance" and "Singapore shopping malls".

"There are hongbao in every room in my house," Madam Chew, 68, told The Straits Times at her home in the Skudai district of Johor.

She has amassed a collection of more than 100,000 packets in red, green and other colours over 12 years from both sides of the Causeway with the help of her son Eric, who lives in Singapore.

Mr Eric Lee, 42, spends up to $3,000 yearly on red packets, posting on online forums and trawling marketplaces like Carousell to get hold of as many unique designs as possible for his mother.

They range in price from $2 a packet to $200 for "premium" ones belonging to luxury brands that sometimes come in elaborate boxes.

Madam Chew and her husband, who are Malaysians and run a cleaning supplies business, sent their two children to live and study in Singapore from a young age.

Mr Lee, who is executive vice-president of magnetic data storage at a materials firm, is married and has a son of his own. He said: "Coming to Singapore to study changed my life course... I love my mum and dad and this is my way of showing I care."

Madam Chew became a serious collector after attending a hongbao exhibition at a Hokkien association in Johor, although her interest began earlier. "I felt like some of the packets were too nice to give away so I started putting them aside, not knowing that people collect hongbao," she said.

She now saves the bulk of her shopping for the festive period in order to obtain the packets from businesses, which sometimes impose a minimum spend.

"There is a mall here that has six designs, one every week. For each design, you have to spend RM288 (S$98), so the whole set will cost you about RM1,800," she said.

"The hobby can get quite expensive; I spend a few thousand dollars every year."

With Chinese New Year just around the corner, Madam Chew has been using both offline and online channels to get her hands on this year's designs. Her husband helps to manage a red packet collectors Facebook group, posting photos of new additions and facilitating trades with its over 2,000 members.

Envelopes are mailed and received daily at their business office, which houses part of the collection.

Madam Chew is kept busy cataloguing new additions, which are sorted chronologically into files themed according to categories such as zodiac animals. There are seven for last year's rooster alone.

"I always have some hongbao with me... I have to put them into sleeves, trim them to size and tape them to the paper, on which I print the year," she said.

Remarkably, she is able to tell on sight whether a hongbao is part of her vast collection.

Among her most prized possessions are leather packets by carmaker Rolls-Royce, given to her by Mr Lee. "Not many people have them... I only have a pair, so they're very precious to me," she said.

"Hongbao designs are getting better and better, and every year there are different ones... Once you're in it, you wouldn't want to stop."