Fortunately, closer examination revealed that the coffin was empty.
A video clip of the coffin floating down flooded Soi Phaholyothin 54 in northern Bangkok has gone viral on Thai social media.
The unused funeral item was finally traced to the nearby Saphan Mai branch of Burapha Coffins.
The shop owner, who asked not to be identified, said on Friday that his neighbourhood was hit by flash flooding after several hours of heavy rain on Thursday.
With the floodwaters rising rapidly, his employees scrambled to move stock from the shop upstairs. But they were too late to save two coffins, which floated out of the shop and down the street.
The items were eventually retrieved but not before someone took a video of the floating coffin and posted it on the Saphan Mai Facebook page.
The shop owner said that people in his neighbourhood were familiar with his business so they had probably realised that the stray coffins came from his shop.
“But I was worried that if the coffins floated out of the neighbourhood, they might scare people, particularly at night,” he added.