The 58-second video was uploaded on Monday by a Facebook user who went by the name Nice's Pumkin. She wrote that she and her parents saw the dog struggling to poke its head out of the window of a car parked outside a hospital in Uttaradit on a hot day.
People who passed by tried to help the troubled dog by pouring drinking water into the its mouth. The dog continued to writhe in discomfort and then suddenly bit its tongue, causing it to bleed profusely.
"My parents and I found out that the dog had been inside the car for about three to four hours and the dog appeared thirsty and in pain. The weather was about 40 degrees Celsius at the time. The dog bit its tongue because it got its head stuck in the window and struggled to breathe," Nice's Pumkin wrote.
She also asked people who have pets to treat them properly.
"The dog survived, but it might not have made it if rescuers came a little later," she wrote.
Facebook user Golf Lor Jang said he was sitting outdoor under an umbrella and it was still very hot. The owner should instead be trapped inside the car, to understand how the dog suffered.
On Sanook.com web board, an Internet user who went by the name Khon Liang Ma (Dog Raiser) wrote that the owner was probably just careless and did not mean to torture the dog.