Gi, 28, grew up in Yuen Long where his family owned a grocery store. He started smoking in Form One and often skipped class in secondary school.
"I was bored with school. Every time I opened my textbooks, I felt sleepy," he says.
"I didn't feel motivated; I preferred to hang out with my friends off campus."
But Gi finally found a purpose at CCC Kei Long College after his friends introduced him to running.
"I had to repeat Form Three, and that year, my friends at school took me to the running track. The coach asked me to run 1,500 metres, and he was amazed how fast I was," Gi says.
That year, Gi broke the school record for the 1,500m. He then got more involved with the track team - and even quit smoking.
"I met many athletes who told me that smoking can destroy a runner's career. So I tried my best to quit cigarettes," he says. "But I have to say, it was a painful process. Running was the only reason I was able to stay firm and stop the bad habit."
Gi went on to win several local races. By then, he viewed school in a different light.
He graduated from secondary school and studied at the Institute of Vocational Education (Chai Wan) for a year. He worked as a teaching assistant at a secondary school the following year.
That's when he realised he wanted to go back to school. "I saw other teaching assistants getting higher pay because they had degrees. This motivated me to study again," he says.
So he went to Baptist University and spent the next five years completing associate and bachelor's degrees in physical education and recreation management. He graduated last year.
Even at Baptist, running was never far from his mind. And he emerged a better athlete, thanks to the university's sports experts who helped evaluate his physical performance.
Gi has competed in two 10,000m and five half-marathon races this year, and the results are encouraging. Last month, he broke the Hong Kong record for the 10,000m at the Xtep Hong Kong Athletics League (Round 2).
In February, Gi won his first half-marathon at the Standard Chartered Hong Kong Marathon, beating last year's winner, Thomas Kiprotich, by 35 seconds.
"I was more than 50 metres behind Thomas after the Western Harbour Tunnel, and I thought it was impossible for me to catch up. I was so tired, but then my determination kicked in," he says.
Gi says he started writing in a journal a few years ago, as a way to remember how far he has come. "I wrote down how delighted I was after winning the title. Now I need to look ahead and focus on new targets," he adds.
Gi currently ranks No 1 in Hong Kong in the 3,000m steeplechase, 5,000m, 10km, 15km and half-marathon. He is also a full-time coach. Last year, he set up the Runners Athletic Club, which offers courses and regular training for middle- and long-distance runners.
"I believe athletes need to find their own targets. As an athlete, I think results are important, but you also have to love the sport," Gi says. "I hope my students will also feel the same way."