Is there a difference between being self-employed and being a business owner?

Yes, your dad is consider as self-employed. First of all, make sure he do up his income tax, pay his medisave arrears.

There's only two distinctions: i) employee ii) self-employed

From IRAS:

• Owner of a business that buys and sells goods and/ or services

• Hawker (you are the owner of a hawker business or a food stall)

• Direct seller

all counts under self-employed.

Source; https://www.iras.gov.sg/irashome/Businesses/Sel...