Mr Lui, originally from Malaysia, said he supported a flag change but would not vote for the Lockwood alternative.
"Unlike Canada's maple leaf, which is steady and balanced on both, our silver fern cutting across the new design is indecisive," he said.
"Even the blue is a lighter blue to the current flag, a mark that the country could get weaker."
Feng shui is a Chinese philosophical system of harmonising people with the surrounding environment.
According to Mr Lockwood, the bright blue represents the nation's clear atmosphere and the Pacific Ocean which all New Zealanders or their ancestors crossed to get here.
The silver fern was a New Zealand icon for over 160 years, he said, and had been worn by many generations.
Mr Lui also said overall, the new flag had "yin" characteristics and lacking in "yang" elements.
"Flags need more yang elements, like having more red and more solid emblems, that would energise and bring strong growth to a country," he said.
"What we have here is a yin flag with a fluttering silver fern that marks instability and no growth."
Voting closes on March 24, and voters are encouraged to post their voting papers back by next Monday to make sure they arrive in time.