* Li Ka-shing to retire after annual general meeting on May 10
* Li will stay on as senior adviser to the group
* Li pledges to don "new battle suit" with charity work
* Son Victor Li will take over the reins of the business (Adds Li's quotes)
HONG KONG, March 16 (Reuters) - Hong Kong's richest man, Li Ka-shing, announced his retirement as chairman of CK Hutchison Holdings Ltd on Friday, bringing to a close a rags-to-riches story that made him a hero in the freewheeling capitalist hub.
Li, 89, will retire after the annual general meeting on May 10, the ports-to-telecoms conglomerate said in a filing to the Hong Kong bourse, passing the mantle to his eldest son Victor Li, who was named successor several years ago.
While Hong Kong's adoration of Li Ka-shing and his story has waned somewhat in recent years, he is still stepping aside from one of Asia's most outward-looking empires, spanning more than 50 countries and 323,000 employees at last count.
A factory apprentice when he was 13, Li, has been called "Superman" for his business acumen and success.
"I've been working for a long time, too long," a relaxed Li, dressed in a dark suit and striped tie, told reporters.
He said the secret to his success included factors like continual self-improvement and unstinting hard work.
"I have always taken the straight path," he said. "I'm very happy and very honored I have had this opportunity."
Li will, as expected, stay on as senior adviser. Victor, who has been a group co-managing director for several years, is seen as a steady hand unlikely to change course.
At the news conference, however, when several questions were addressed directly to Victor, Li ended up interrupting his son with his own answers.
During his tenure, Li Ka-shing increased the pace of overseas acquisitions, helping boost the group's profits with growth in the European telecoms business offsetting a drop in the value of the British business following Brexit.
Through his flagship CK Hutchison, Li controls the biggest container port operator in the world, Canadian oil giant Husky Energy Inc, one of Europe's leading telecoms operators, as well as infrastructure assets and a long-time interest in Britain that saw him awarded a knighthood in 2000.
"Li Ka-shing is remarkable - he's a role model and I regard him as such," said Stuart Gulliver, former CEO of HSBC who in a 38-year career with the bank worked closely with Li.
It was HSBC's 1979 sale to Li of a stake in Hutchison Whampoa, a colonial-era trading house, that vaulted him into the first rank of Chinese tycoons.
Commending Li's long laid-out succession plan, unusual among tycoons in a region where discussing death is often viewed as unlucky, Gulliver praised Victor for being extremely capable.
Reinforcing the view that the transition will be seamless, Victor said: "Tomorrow morning when I go to work there won't be any difference ... (My father and I) are also upstairs-downstairs neighbors, how could we not chat?"
STRONG RESULTS AT LI'S COMPANIES
The news of retirement came together with the announcement of better-than-expected results at some of Li's biggest firms.
CK Hutchison reported a 6 percent rise in 2017 profit to HK$35.1 billion ($4.48 billion), versus the average forecast of HK$34.63 billion from 12 analysts polled by Thomson Reuters.
The real estate arm CK Asset Holdings Limited saw annual profits surge 55 percent, also beating estimates.
"Healthy and synchronized growth in major economies gathered pace in 2017. Provided this trend continues and inflation remains benign, the environment in 2018 should remain supportive for global trade and for our businesses," Li said.
He declined to forecast, however, whether the red-hot local property market, one of the world's most expensive, had peaked.
"I dare not speculate on property prices ... property prices have gone out of reach for the public," he said, while urging the government to build more public housing.
Li, who ranked 23rd on the world's rich list by Forbes, is the wealthiest tycoon in Hong Kong, a former British colony that returned to China in 1997.
Over the past few years, Li's close ties with Beijing's Communist Party leadership have come under scrutiny. He has never been publicly over-critical.
"I like to read history very much... and about my country. If I can vote today, on the constitutional reform (in China) so (President) Xi (Jinping) can go for another term ... I will vote for him," Li said.
"My relationship with the central government is pretty good. But personally I don't say things that I shouldn't say."
Despite his retirement, the sprightly Li said he would not completely rest.
"I will don a new battle suit and put all my efforts into the work of my (charity) foundation, especially on the aspects of medicine and education."
CK Hutchison shares closed up 0.3 percent on Friday. ($1 = 7.8432 Hong Kong dollars)
(Additional reporting by Jennifer Hughes and Carmel Yang, Writing by James Pomfret; Editing by Nick Macfie and Himani Sarkar)