"If I didn't learn to play rugby," the 23-year-old says, "I may have hooked up with gangsters or even become addicted to drugs."
As a teen, Lam says, he lost his way- and it was rugby that helped him get back on the right track by giving him a purpose.
A migrant from the mainland, Lam came to Hong Kong at the age of 11 and began studying in primary two. "I didn't like the city," he recalls. "I told myself I didn't belong here and I found life in Hong Kong pretty boring. I didn't want to stay."
After a month, he bought a ticket back home with money from his Lunar New Year red packets. Yet his relatives on the mainland sent the boy back to Hong Kong.
By 2003 he was getting in trouble at school, starting fights with other students. The troubled teen even came to the attention of the police. Yet this would prove to be a blessing in disguise.
"The police's Community Relations Bureau had a trial scheme called Operation Breakthrough in Wong Tai Sin district," Lam recalls. "They worked with the Hong Kong Rugby Football Union to promote rugby for teens with behavioural and discipline problems."
Police officers urged Lam and members of his gang to join, but he turned them down first. After a while he gave in to his friends and joined the programme.
"Police officers volunteered to teach us how to play rugby," Lam notes. "I was touched by their dedication. We were teens in trouble but they showed us respect."
Lam, then 15, fell in love with the sport. He started training hard and soon became a key player for his team.
He was just 17 when he was invited to play at a senior tournament. The Police Rugby Football Club invited him to join their team for their games in the third division league competition.
"I was very happy," Lam says. "I learned a lot during my two-year stay with them. Then I moved up to the second division to join another team, Nomads Rugby Football Club. They are targeting a place in the first division with a new team and I will be on it."
Thanks to rugby, Lam has managed to turn his life around. He has also turned from a brooding teenager without goals to an upbeat young man with a passion for life.
Now, he wants to use his own experiences to guide other troubled teens onto a safe path. Two years ago, he began coaching in a youth rugby training course called "Don't drop the Ball."
Like Operation Breakthrough, the programme is co-organised by the Rugby Football Union and the police. The initiative promotes rugby in schools.
Students don't need to have discipline or behavioural problems to join. "All we want is to give them a good hobby so that they won't 'drop the ball' in their lives," Lam explains. "In other words, we want to keep them away from drugs and crime."
Lam and his fellow instructors have managed to get several students to join the initiative and develop a passion for rugby.
"Some schools have decided to set up their own teams. So now we even have an inter-school rugby tournament," Lam says.
As for himself, he lives and breathes the sport. "I spend most of my time training, playing or teaching rugby," he says.
The rest of his time he spends studying for an associate degree course at the Hong Kong Institute of Education.
He may have his hands full, but he likes it that way. "Working for DDB is meaningful to me," Lam says. "Rugby has saved me from a possibly very bad ending. I've learned to be more considerate and not to be selfish. I've also learned discipline."
His goal is to teach those positive values to other youngsters, too.
For details of DDB programme, visit www.youth.gov.hk/en/special/ddb