JUST last week they changed all the major street names in Phnom Penh. It was an interesting exercise and goes to show how rapidly something similar might be done here in 1997. Apparently Prince Sihanouk announced that the two major thoroughfares would be known after Khmer royal names, Norodom and Monivong, and no longer after a couple of unloved leftists from the high days of the Vietnam-backed regime. The Prince, not known for dwelling on one subject for more than a couple of breaths said of plans for the rest of the city map simply ''et cetera''. The interpretation of the royal ''et cetera'' has been joyfully wide. My hotel, the ancient and venerable Renakse, woke up to find itself no longer on Boulevard Lenin but Boulevard Saigon. It is interesting to see how many political swipes one name change can pack. Boulevard USSR, which looked set to survive its namesake for ever, gave way to Pochentong. Just a few blocks away, in an act of anachronistic whimsy which has brought tears of mirth to the eyes of many and could only be The Prince's, the Achar Hemcheay is now Boulevard Charles de Gaulle. Many of these streets still represent a French colonial city in aspic. Nothing much has been built since Sihanouk's original time. The only structure of flashy black glassed vulgarity over a couple of storeys is called The Hong Kong Centre. I wonder who could be behind that? Charming though these streets are in the daytime, they tumble into pitch darkness at night. The 20-year-old street lights are there and mostly upright but nothing powers them. Not many people are out under them either. What might appear to the new arrival as a delightful stroll home under the stars is known to residents as an act of folly. I was daft enough to suggest it saying goodbye one night to the proprietor of The Cafe No Problem. He paused. ''Ah, non. I would not do that. You might scuff your shoes on the bad pavement. Take a cycle.'' What he was really saying was: ''You might not even be found until morning.'' Cyclos are slow, somnabulent but lately unpleasant on the wider streets submerged under the arrogant exhausts of the UN jeeps. At night they have an advantage. If the driver is paid well, he is looking down on an important meal ticket. It is in his interest to do what he can to keep the passenger's lungs opening and closing as frequently as his wallet. And nobody steals cyclos. With exceptions, they are held together by the rust of two decades. Motorbikes on the other hand are held up at gun point. A recent article in the Phnom Penh Post pointed out that, once the hold up is achieved, the bandits are increasingly careless of what to do with the riders. Even if the surprised fellows make the best of a bad job and offer up the machine, robbers are opening up on them anyway. The point of Phnom Penh is charm spiced with unpredictability. On my last night there, I threw travel guidelines to the night airs and jumped on the back of a Honda owned by an English colleague. He assured me that it was so old, we would have difficulty giving it away to gunmen. Since we fell off twice trying to dirt ride on waste ground by the Tongle Sap River at dawn, it is no longer likely to be in any condition to be on offer. We went to night clubs that roared under the patronage of the free spending UN and look like whimpering when they have all gone home in a few weeks. The car park attendants carried AK-47s. The UN soldiers carried guns. The Wild West and the National Rifle Association had nothing on it. An Australian sergeant, packing a pistol and a pint, demonstrated how being in a war zone focuses attitudes. ''That bastard Keating,'' he declared democratically, ''may think he is getting rid of Queen Elizabeth but he'll have me and the Forces to contend with if he does. I know which corner of that flag I am fighting for!'' As a ''Pom'' that or the Russian vodka at throwaway prices was making me feel warm inside so I did not pay much attention to where we were biking to next. It was a small chalet brothel on the edge of the city's Boeng Kak lake. The purpose was journalistic curiosity, of course. But it ended soon enough. Three neat stern-faced young men came in and sat down opposite, just watching the very little there was to see. I looked across to my colleague enquiringly. ''Khmer Rouge,'' heexplained quietly. ''Keep smiling. They own the place.''