ALTHOUGH his name was conspicuously missing from the Queen's Birthday Honours List yet again, Hongkong's richest man, Li Ka-shing, received an unexpected birthday present from the bible of capitalism, Fortune magazine, a few days ago. And, as the Cheung Kong chairman sits down to celebrate his birthday with his family today, he will be happy in the knowledge that his net worth has been assessed at $45 billion, making him the 16th richest man in the world, according to Fortune. With 35 per cent of Cheung Kong Holdings, his investments include securities, real estate, oil, container terminals and communications. This being his birthday, what exactly could Mr Li buy with all the wealth, if he were to liquidate his assets tomorrow? If he were in a generous mood, he could buy everyone in the world, all five billion people - give or take a few hundred million - a Big Mac at a McDonald's of their choice, and still have $5 billion left over for some fries. Or he might like to treat himself to a couple round trips on the space shuttle - a bargain at roughly $6.3 billion. He could buy 29 Boeing 747-400 jumbo jets at $1.17 billion each (last year's prices) and start his own airline. If he preferred boats to planes, he might want to buy a fleet of Italian-made Azimut yachts, said to be the finest money can buy at $49 million each. After setting sail, Mr Li could enjoy lashings of Buluga Caviar, at a mere $640 per 50 grams, the best sharks fin soup money can buy at $500 per serving. To wash it all down he could have Dom Perignon champagne at $11,280 per crate. However, this fare might be too rich for a tycoon with down-to-earth tastes, despite his huge wealth. ''My philosophy is so simple, I enjoy very simple food, dress very simply . . . my car and living standards are the same as they were 20 years ago,'' Mr Li said. ''You don't spend for yourself one penny, but you don't mind spending $100 for your friends.'' That is Mr Li's creed. Being the friendly sort, he might, perhaps, want to help out fellow tycoon Donald Trump by buying the Taj Mahal casino, at $7.7 billion, and also take over one of the major American Airlines now flying under Chapter 11 bankruptcy protection. If he fancied the idea, he could help out the Hongkong Government by plunking down the cash to pay for Chek Lap Kok airport outright. Mr Li could afford to purchase nearly 12 luxury office buildings equivalent to the $3.8 billion he paid for his newly acquired 9 Queen's Road Building; that is more than half of Central. Putting things in perspective, Mr Li's billions could have financed about 67 per cent of last year's re-exports from Hongkong. As Fortune pointed out, regardless of how he ''spends'' his birthday, one should keep the following in mind: invested in a conservative, 30-year, triple A-rated, tax-exempt municipal bond yielding a mere 5.6 per cent, $1 billion would shower Mr Li with $153,425 in interest every day. Then again, he may like to better his chances with next year's Birthday Honours List by helping out the Queen with a small cheque for $723 million to restore Windsor Castle.