When you think about it, the fear of fireworks for animals, is basically the same as it would be for humans, but more painful,
Animals, perceive sounds much louder than humans because they can hear better. so the noise can be painfull for them,They associate such noises with danger, and all their (survival-) instincts tell them to run to a place of safety.
The flashes of light produced by fireworks seem just as threatening as the noises.
What’s more, the lights and noises are accompanied by smoke and acrid smells.
The noises and lights from fireworks can trigger an animal's fight-or-flight response.
I think if i was that elephant and fireworks were let off near me i would run !! but Thais do not think about the consequences of there actions or about the safety, all they think about is money!