Does Ha’anaka applies to a part time worker too?
The halachos of Ha’anaka do not apply nowadays, because this mitzva only applies to to a master giving his Eved Ivrei (Jewish slave) presents when his six years of work are finished. It does not apply to any workers nowadays, (even if you feel like a slave). Nevertheless, if the local laws require an employer to give severance pay to a worker, even if he is only a part time worker, he is obligated according to halacha to do so.
Sefer HaChinuch- Mitzvah 482.