The police arrested 16 suspects under 15 years old and two older than 15 on a road along an irrigation canal in Tambon Nam Phrae and seized 14 motorcycles.
Police carried out the operation after local residents complained that the youths had been closing the road and using it for racing on many nights, making loud noise that disturbed their sleep.
Police said the arrested boys belonged to two major gangs in Chiang Mai, called "So Hot" and "Black H9". Police said the gangsters lived in San Pa Tong and Hang Dong districts and often organised road racing.
They were charged with racing motorcycles on a public road and using illegally-modified motorcycles.
Police also sought a court order for confiscation of their motorcycles.