BANGKOK (AFP) - Thai police on Wednesday said they had charged five defrocked Buddhist abbots with sexually abusing eight boys at monasteries around the northern city of Chiang Mai.

The abuse was discovered after police rescued one boy from the abuse ring last year, police said, adding that all the children involved were under 15 years of age.

"Four of the abbots volunteered to disrobe, but one denied the charges and was forcibly defrocked," Major General Prachuab Wongsuk, of the northern police region, told AFP.

He said police found alcohol and pornography during a search of living quarters at five monasteries. Police believe the abbots were acting together and Prachuab predicted that more monks would be arrested soon.

Those charged face a maximum of 20 years in jail if convicted.

Monks in Thailand, where some 95 per cent of the population are practising Buddhists, have been hit by a series of scandals, with local media reporting cases of drug-taking, drinking, gambling and visiting prostitutes.

In September, authorities seized nearly US$800,000 (S$1 million) worth of assets, including a Porsche and a Mercedes-Benz, from a monk who was defrocked for a controversial trip in a private jet and who was also accused of fathering a child by an underage girl a decade earlier.