FROM time to time, danger zones for Japanese travellers flare up and throb for a while, doing no end of damage to the ozone layer. One used to be the car park of pak pais at Bangkok International Airport where one Japanese tourist, had he lived to do it,could have complained to the tourist police of being taken on an indirect route and overcharged down to his gold fillings. With an awful predictability, Cambodia became a danger zone for Japanese, as has practically any American suburb. I do not know how anybody in an American suburb survives from one Halloween to the next. Apart from the locally grown robbers, rapists and murderers, crazed from years of clean sidewalks, neat front yards and taking out the trash, there are the visiting day-trip gangs from the ghettoes offering features from Stephen King horror novels. Resurrected child murderers, escaped mental patients with superhuman powers, clowns who bite peoples' limbs off and make the bathroom taps run with blood, and pet cemeteries which do unpleasant Lazarus jobs on deceased Fidos, all stack the odds impossibly against the not-quite virginal Charlene, setting out on her first date with Chuck. If Charlene has a Japanese exchange student staying with her, the entire family will have its bodily juices drained by fast-moving ectoplasm and the house will be sucked into the ground by an undiscovered graveyard of burnt witches. To these Japanese danger zones, Tsim Sha Tsui (or ''Jim's so chewy'' to new expatriates) is discreetly adding itself, through tiny items tucked into those ''news in brief'' columns which you winkle out before confessing that you have indeed read the whole newspaper and will be forced to start work. On Monday, a 42-year-old Japanese tourist was knocked unconscious by two men in Tsim Sha Tsui and robbed of his $100,000 watch, his credit cards and $8,000 in cash. I suspect that this was the work of those Nathan Road copy-watch cowboys putting their expertise into reverse and spotting the real thing a block away. It figures. I have never seen one actually sell a copy-watch and I have puzzled over what they did for subsistence. Japanese, that's what. The incident should be noted by the blase gweilos who sit in their recreation clubs behind barbed wire, and martial art-like Sikhs with hockey sticks, declaring that, in Hong Kong, you can walk anywhere at any time without fear. Not if you live in Tse Wan Shan you can't; or if you owe money to loan sharks; or if half the estate is another gang's turf; or if you are a Japanese in Tsim Sha Tsui. This sort of assault puts tacky Tsimsy into the league of Victorian gas-light London. ''An isolated incident,'' I hear the Tourist Association panting as it dashes, breathless, to the scene. Not at all. A mild one actually compared to the experience of Mr Tsutomo Watanabe, which I doubt you would find again even in Lagos or Kafka. Mr Watanabe came to Hong Kong hoping to see a woman he had met here before, one of the few sound motives for a repeat visit. Foolhardily roaming Tsim Sha Tsui in his search, he was robbed there and, mark you, stripped of his clothes. A desperate band indeed. Understandably disturbed by this, Mr Watanabe reportedly swam across the harbour - and lived. To be fair to Kowloon side, he was robbed all over again on the island, though of what by now, I cannot imagine. Naturally taken by a cab to the wrong hotel, and penniless, he slept in the street. Mr Watanabe clearly needed police help and, wet, naked, showing the signs of two duffings-up and flat out on the pavement, you would have thought he would have got it. According to his defence counsel, to attract attention, it was necessary for him to drive a brand new Porsche through a showroom plate-glass window into the street and then some way. He is recovering in Siu Lam Psychiatric Centre and Tokyo may be drawing a red ring around us on the map. It is a relief that Michael Jackson did not come after all. He is not Japanese, at least he has not said he is yet, but he would inevitably have been staying in a well-known Tsim Sha Tsui hotel. On a sensitive man who takes morning baths in road marking paint, succumbs to dehydration and migraine in a week, Tsim Sha Tsui and a police force that stages 5am hotel raids would have taken their toll.