Raiding the Oon Aree community in Chiang Mai, the authorities arrested more than 30 illegal immigrants workers who built shelters in the area.
Some workers had illegally entered Thailand, while others left controlled areas to work as construction workers, or in restaurants. Some have been involved with illicit drug networks.
The authorities pulled down nine houses which intruded into the Mae Kha Canal near the Pa Paeng and Sri Mongkol communities, a hideout for illegal immigrants.
They also dredged the canal to clean up the water sources in the area.
At least 40 other houses were found encroaching into public places along the canals. The authorities are to further negotiate with building owners to reclaim the areas.