But, he argues, "if you try to say I won't allow an investment to take place... until the investor's system is totally transparent - I think you've missed the boat."
Tsang argues that the "initial suspicion of some receiving countries" will diminish. "People have to realise we are now living in a very globalised world" and trade and investment flows should defy political boundaries.
Tsang was in New Zealand on the first leg of an international swing that takes him on to Chile and Brazil to promote Hong Kong as the gateway to mainland China.
He says he "treasures" the closer economic relationship Hong Kong has forged with New Zealand - its first partner in a free trade agreement. Bilateral trade has reached US$1 billion ($1.22 billion) and is growing by 11 per cent a year.
While Hong Kong's domestic market of 7.5 million people is clearly bigger than New Zealand, "by global standards it is very small but the China market is enormous," says Tsang. "China is going through a phase where the economic growth will rely more on domestic consumption... replacing the export dependency which has been the trend for previous years - this will all happen in the next three, five or 10 years when China will clearly emerge as an economic superpower."
He argues that areas in which New Zealand excels - things such as high technology, geothermal energy and agricultural products - are "precisely the sorts of things" China will need for that next growth phase.
Tsang is also keen to promote Hong Kong's ability to assist New Zealand firms get into the bigger market.
"We have been the largest investor in China in the last 30 years since the opening of China," he says.
"We have the best networking of economic pursuits on the mainland. We are also the premier international financial centre for East Asia and have the ability to help medium-sized enterprises and even small enterprises on the mainland."
The growth of the renminbi trade has been a runaway success since China began settling international trade in its own currency, to reduce exchange risk.
Three years ago, almost all China's trade was denominated in US dollars. Roughly 9 per cent of that trade is now in renminbi yuan, almost all of it cleared and settled in Hong Kong for China as a whole.
Remarkably, the volume of trade has grown 1000-fold in two years, from RMB1.9 billion to RMB1.9 trillion.
Tsang says Hong Kong has been very successful helping foreign firms raise renminbi to settle trade in China. "But I haven't seen any New Zealand firms do that. Only one has done a little dim sum bond issue."
He also wants to see New Zealand firms listing on the Hong Kong Stock Exchange, not only as a way of raising funds, but also because it will give them a profile with the many mainland investors.
Lately, however, the Asian financial hub has been rocked by high-profile corruption investigations which could potentially mar its reputation as a "clean" place to do business.
Hong Kong's Independent Commission Against Corruption recently arrested former chief secretary Rafael Hui Si-yan and the joint chairmen of Sun Hung Kai Properties, Thomas Kwok Ping-kwong and Raymond Kwok Ping-luen. Reports suggest investigators are probing alleged malpractices involving the developers' huge holding of undeveloped rural property. But charges are yet to emerge.
"The Kwok case is one out of the blue and I am not supposed to talk about cases," says Tsang. "Because it hasn't gone to court yet, it is unfair to the parties concerned."
Tsang maintains that Hong Kong has a "very clean system" with low or zero tolerance for malpractice of any kind. "When incidents like this surface, the only thing to prove that we remain so is to tackle these things through a court."
The anti-corruption commission would take any case it believed was malpractice to court, regardless of the status of those involved; "I think that is the strength".
The commission is also probing Tsang himself, following claims he was the beneficiary of favours from local business tycoons, including being allowed to lease an apartment for below-market price. "The fact I rented a place outside Hong Kong I would not see as corruption," he argues. "People say, well, you just stay in Hong Kong, why should you rent. And then people believed it was the wrong thing to do and portrayed it as some form of malpractice."
With the handover to his successor, Leung Chun-ying, fast approaching, it seems a good time to ask if Hong Kong's laissez-faire regime is at a crossroads.
"I hate the word laissez-faire," says Tsang. "We believe in free markets but any government needs to intervene [in some areas] when the market fails to operate."
He cites the housing market, where the Hong Kong Government has been intervening for the past 15 years. "But in terms of commercial practice, we try to avoid anything which the private sector can do.
"It must be left to the private sector - the dirty fingers of government should not be in it at all. That's my belief.
"By constitution we are supposed to run as a capitalistic society. We'll continue to do that."
But he concedes there are political pressures for more welfare and other social spending. "This is inevitable in a first-world country."
On July 1, Tsang hands over the reins after eight years as chief executive and will then retire. He has spurned offers of commercial directorships. "I am 67, pushing 68. I am going well beyond my working shelf life. I used to hope to retire at 55 and find a second career, but I have been working full steam for the last 45 years."
His predecessor, Tung Chee Hwa, is now Vice-Chairman of the National Committee of the Chinese People's Politics Consultative Conference. Tsang says that if "the motherland" asked him to do something which drew on his expertise in finance, markets and governance, he would do it.
For now, though, he has done enough public service. "I am a serious photographer - I really want to do something while I am still mobile. I have an ambition to go and photograph migrating birds and wildebeest."
He's also looking forward to spending more time with his wife and grandchild and studying the Bible in two very difficult languages - Hebrew and Ancient Greek: "I know I won't be able to finish the alphabet before I reach the grave. I shall be busy but I hope in a very quiet and personal and satisfying way."
