The Chiang Mai Irrigation Office will start plucking krathong garbage from the Ping River on Tuesday.
The office explained that it would wait for the Yi Peng festival to end before it would collect krathongs from the river.
The festival began on Saturday night. On the following morning, a lot of krathong garbage was trapped at the watergate in Tambon Pa Daed, Mung district.
The irrigation office opened just one panel of the gate to direct the krathongs to flow into the same spot.
Officials also set up a giant frame for krathongs to flow into.
Workers at the irrigation office estimated that there were about 4 or 5 tonnes of krathongs in the river now and 90% were made of degradable materials, such as banana leaves and stems.
Last year, about 30 tonnes of krathong garbage was plucked out of the water.
Officials said the collected krathongs would be sorted out for materials that could be used to make compost and the rest would be later disposed of.