The 47-year-old angry father of five was also fined the equivalent of about $2,500 during his July 19 sentencing.
The nine-year-old boy was frightened enough to urinate where he sat after the man struck him, and displayed a red and swollen left cheek, according to court documents.
Prosecutors outraged at what they say is too lenient a punishment for the father's actions are demanding a higher fine and a longer sentence, claiming that the boy now suffers from recurring nightmares and can no longer attend the school.
In lodging an appeal, prosecutors claimed that the judge who handed down the verdict was "overly lenient" and "glossed over" the father's "violent conduct," and ignored a previous conviction for assault with a deadly weapon, according to Channel News Asia.
After calling the punishment "manifestly inadequate," the public prosecutors implored the appeals judge to reexamine the case.
A High Court Justice agreed to the demands of the prosecutors, noting that the father "had no business entering the classroom at all, let alone confronting the boy in front of the entire class and their teacher," reports Channel News Asia.
In agreeing to reexamine the case, the new judge observed that the angry dad "self-righteously justified his conduct by, ironically, ‘lecturing' the entire class of impressionable young children that it was wrong to bully others or to behave like [a] gangster."
"What is especially aggravating is [the father's] deplorable violation of the sanctity of the school environment and the distress and disquiet caused to the children and their teacher," added the appeals judge.
For causing hurt with malice aforethought, the father could be jailed for up to two years under Singaporean law.