Just as the hero of The Mentalist - the hit American detective television series shown in Hong Kong - involves a man using observational skills, such as body language, to solve crimes, Billy, 16, has become a "mentalist" to help him face tough opponents.
Billy, ranked 14th in Hong Kong in the Under-18 boys' category, had previously struggled when taking on players from the mainland. But not any more.
He learnt how to size up his opponents while at last month's All China Secondary Schools Students' Games in Baotou, in Inner Mongolia.
In the main hall, with many different matches going on, he was able to watch many of the players in action.
He realised that mainland players, for example, adopted similar methods while playing - when changing to an attacking or defensive style.
He was able to react when spotting the tell-tale signs that the player was switching tactics - and anticipate and respond better.
The former wushu devotee became interested in table tennis at aged seven, after watching his friend's father playing the game at Kowloon Park Sports Centre.
"I had never seen people playing this sport," Billy says. "It looked strange. My friend's father let me try to hit the ball - and I was hooked on the game."
He found he had a natural talent for the game and won many primary inter-school competitions. "I have won many titles; I was a very strong player at that time," the Form Four student at St Paul's Co-Educational College says.
Yet Billy's progress faltered when he reached secondary school. He began to lose most matches he played, including those contests against players he had beaten when he was younger.
"I started to question my ability and performance," Billy says. "I became much more nervous in matches because I desperate to win and prove that I was still a good player."
He had been a regular member of Hong Kong's junior table tennis youth squad for years, but a few months ago Billy chose to leave the team because of the clash with his school studies. "Afterwards I suddenly felt more relaxed and had a new mindset when playing games. I started to play better and win more competitions," he says.
Billy, and Leung Hui-hong, his schoolmate and doubles partner, surprised many people by reaching the semi-finals of the Hang Seng All Schools Championships in June. They were narrowly beaten by the La Salle pair, Lam Siu-hang and Hung Chun-hin, after holding their own match points. But this improved form earned him a place at the games in Baotou.
Billy and his teammates made a slow start, losing their two opening team matches. But then, after Billy had watched the body language of some opponents in action, he adopted a tougher mental approach to help outwit them, Hong Kong to start winning.
"I have always been determined to win, but that was not enough to play well at the Games. So I started watching how some opponents handled the big points - or switch tactics; that helped me to predict what they would do in my matches and I was better able to respond."
He impressed spectators with his dynamic play and helped Hong Kong recover from their slow start to finish a creditable 10th out of 15 teams. He played very well in the singles, too. He beat a leading Beijing player in the last 32 - fighting back from two sets down to win 3-2 - before losing another five-set tie to a Shandong rival in the last 16.
"My mainland opponents were much better than I, in terms of serving and returning serve. But I used what I had seen earlier and it worked well for me in matches... I hope to continue using it in future competitions... it has given me confidence to be able to compete against the best players."
Billy will compete again for Hong Kong in the junior competition at the Nikon Hong Kong Junior & Cadet Open, which starts tomorrow at the Queen Elizabeth Stadium in Wan Chai.
For details, go to www.hktta.org.hk/2011hkjo/