Chiang Mai International Airport officials said 81 flying lanterns fell on to the runway on Friday night and early Saturday.
Loy Krathong revellers in Chiang Mai floated the lanterns as part of their long-held Yipeng tradition.
The officials said there were three lanterns with diameters larger than 1 metre, and 74 of them had diameters between 0.5 and 1 metre. The other four were smaller than 0.5 metre.
The Yipeng tradition continues on Saturday, and officials have called on revellers to float their lanterns only between 7pm and 1am.