We heard people closer to the sign screaming and the crowed swayed, pushing people over," the 21-year-old said.
Video footage from the night shows people screaming and running after the sign reading "Happy New Year 2017" was lit up.
"I yelled at my friends to duck. I dropped to the ground and curled up in a ball covering my face to protect it from being burned," Reidy said.
"We think the female tourist next to us broke her ankle after being trampled on by the crowd."
Another Kiwi, from Christchurch, posted about her experience on Facebook.
"So glad we were closer to the stage ... still got burnt/trampled on though.
"[Friend] has a video when we all fall to the ground and you can hear people yelling and screaming and sparks hitting there faces and me like wimping in pain we are fine ... so scary!" she wrote.
It is estimated that about 20,000 people were attending the party on Koh Phangan, an hour's flight from Bangkok.
As many as 30,000 people attend the famous rave every month, which goes past dawn.
Most are tourists from Europe and the United States who have come specifically for the event.
"It was just like a shower of burning sparks," Lucy Coyle, a British tourist, told AFP.
