Shocked cabin crew posted photos of the bloody aftermath on social media, which reveals a seat stained with blood from an injured passenger who hit his head after bouncing off the roof of the plane.
Thai news site Khaosod said he was not wearing his seatbelt when he was thrown from his seat during the flight.
Passenger Sarah-Jayne Edwards, 39, who was travelling with her daughter, AsiaLilly, told MailOnline Travel she wrote a note to explain what had happened to her husband.
It said: "That was THE most scariest flight of my life. Two hours in and we had awful turbulence and no notice.
"We went up and down several times, everything went flying to the roof. People cut their heads, it was sooooo frightening.
"I grabbed AsiaLilly and cuddled her and told her we had hit a raincloud so it was going to feel like a rollercoaster.
"Broke my heart when she said "mummy I'm scared!"'
A statement from Thai Airways was posted on their Facebook page on Monday confirming that six people had been sent to hospital.
Thai Airways President Charamporn Jotikasthira said: "The company apologizes to passengers who were involved in the incident.
"The company has paid the cost of medical treatment for passengers and staff injured.
"All those who were hurt on the aircraft have returned home from hospital."