I'm working as a teacher in a kindergarten, after 4 years, due to some reason, I've decided to leave.

I've already summit-ed my one-month notice (month ago) and today should be the last day of that one month (30 June).
However, my boss still assign many tasks for me and said If I can't finish it, I might need to go there and work for her on the following days (tomorrow, 1 July and so on).

My question is, are she having the right to do so since I'm not her employees anymore? Also, she is keeping my remaining EPF and salary, I afraid that I can't even get it without the job done.

Agree with the others, this is quite BS

I would quite laugh at the face of the boss really, he is just trying to threaten you

Official last day is 29th of July, end of the story, world can die and company burn on the 29th afternoon, officially you do not have obligation to work for them after that.
And they have to give you full money and all since you did your side of the work.
Just to check, the stock issue, is it due by some error you did?
If so then can negociate, but otherwise not.

After that if the boss wants to make some special arrangements with you to work a bit more to finish some added work or something, it's really up to you.
But then you guys both decided on arrangement (money, time etc.)