For the last 10 years, hundreds of people have been gathering at Bishan Park II every Sunday morning for a free workout led by a most interesting fellow.
Tall, tanned and with a complexion marked by acne in his youth, Mr Wong Yoke Seng, 58, teaches 312 Meridian Exercise - a 90-minute routine which involves breathing techniques and massaging key points of the body to activate good blood flow and energy.
It is not hard to pick him out from the crowd.
He is the man everyone acknowledges and greets with a smile, a wave or a slight bow of the head. They call him "Huang laoshi", the latter being the respectful Chinese term to address teachers.
Blessed with a natural ability to rally and galvanise, he has always been a bit of a Pied Piper. But he has not always channelled that to good use.
When he was young, he inspired awe and fear as a hoodlum and a gang leader in Malaysia, and that once landed him behind bars.
A series of dramatic developments in his life including penury and several brushes with death forced him to take stock, and get on the straight and the narrow.
He gave up a successful electronics business about 10 years ago to found Yanhuang 312, specialising in traditional Chinese health care and therapy. The company has five branches in Singapore.
"In the past, I would do anything for money. But I never slept well because I always feared the law or my enemies would catch up with me. But after going on the right track, I've not only helped others but also myself. I sleep well now, my health is good, and people respect me," he says in Cantonese.
Like the popular Chinese proverb, his life story is longer than a bale of cloth, and vibrantly hued.
The eldest of nine children, he spent his early years in Setapak, a tin mining and rubber-growing area outside Kuala Lumpur.
His father was a gang leader who wanted to turn over a new leaf after getting married.