Contrasting with the accepted economic tenet that rising prosperity automatically drives out the substrata of street poverty, Bangkok is experiencing an explosion of organised gangs preying upon its population.

When they are not stalking unsuspecting pedestrians, the gangs are pickpocketing bus commuters or tricking travellers out of their tour money.

''It's a vicious cycle, like the life of bacteria,'' a police commander wryly commented after finding the same syndicates recurring in dozens of street scams.

The sharp differences in wealth between urban and rural areas of Thailand are blamed for the influx of poor villagers - mostly teenagers - who are recruited by gangs.

Some come from as far away as India, Bangladesh, Pakistan, Burma, Laos, Cambodia and southern China, often arriving on cheap air tickets provided by the gangs in return for a cut of their ''earnings''.

A police chief warned recently that the operations were organised ''on Italian Mafia lines'', though their targets were a little more modest: peddling sweets, fake cold relievers and soft pornography, stealing and begging.

A crime taskforce found that virtually all street beggars were trucked in daily by syndicates and deposited at footbridges and bus stations.

Some were found to be housewives ''after extra money'', who were told to pose with drugged babies (usually not their own) to attract public sympathy.

''We earn about 400 baht [HK$125] a day for sitting around and looking sad. It's not difficult work,'' one woman was quoted as saying.

Not even garbage bins are safe from the syndicates. City government officials found an organised racket dividing up the spoils of rubbish thrown out by wealthy households in the residential Sukhumvit Road area.

''There is a war going on between street sweepers and garbage collectors for the best pickings - everyone wants to work in the rich areas, because the rubbish is of better quality,'' said a deputy city governor.

The refuse is sent to recycling plants or repaired and sold off by dealers in second-hand goods.

Pick-pocket gangs provide their recruits with a smart uniform designed to blend in with the fashionable young office-workers who are their main source of income. The tactics vary little from those used elsewhere, but there are some distinctive refinements.

One victim told newspapers of a new racket that takes full advantage of the Thai virtues of honesty and fair play.

''I was on my way to work when I saw a woman's handbag that had been left on a seat. As I was about to pick it up about two stops later and hand it to the driver, the woman got back on the bus with a man dressed like a policeman and called me a thief,'' said the man, an office clerk.

''They forced me to hand over all the money in my wallet or I would be arrested. It was only when they left that I discovered he was not a policeman at all.'' The government has responded to the epidemic of petty crime by in effect outlawing begging. Busking with musical instruments or otherwise entertaining passers-by for money will be allowed, but not soliciting.

Gang organisers face a six-month jail sentence, increasing to five years for those caught procuring young children, and recruits will be sent to vocational institutions ''to make their lives more worthy''.

This is regarded as a typically Thai way of dealing with the moral dilemma over how to help those who prey upon society's most intrinsic values while holding true to one's own religious beliefs.

''Buddhism is already under threat from consumerism and greed and there is no place in religious tolerance for dishonesty,'' a Thai newspaper commented.