There is no Thumper in the original book. That was added by Disney and thus still under copyright until 2042.
Bambi Gets The Horror Movie Treatment In Bambi: The Reckoning

When Felix Salten’s 1923 novel Bambi, a Life in the Woods entering the public domain in 2022, it was only a matter of time until someone turned that source material into a horror film. Three yeas to be exact. The is the trailer for Bambi: The Reckoning, produced by the same team who previously made Winnie The Pooh: Blood and Honey. In theaters July 25th.

“After a mother and son get in a car wreck, they soon become hunted by Bambi, a mutated grief-stricken deer on a deadly rampage seeking revenge for the death of his mother.”

Sure, but any story where the main character’s mother is murdered makes for a pretty easy adaptation into a revenge horror flick. This movie practically wrote itself. Although if I’m being honest, the 1942 Disney version was already horror enough for me. Bambi’s mom getting gunned down, getting chased by dogs, and a forest fire? Come on, I’m trying to sleep at night.