Is it right to submit a conference abstract knowing that I will not attend but my advisor will give my talk instead? My postdoc finished 9 months ago. My former supervisor has asked me to submit an abstract on my work to a conference next year. 

No-one intends that I will attend the conference. My ex-supervisor has an invited talk there, and basically wants current and former group members to also submit contributed talks that  can also be presented  if the main authors don’t show up. 

The supervisor essentially wants to be able to give three or four talks for the cost of one attendee.  I don’t really feel this is right. On the other hand I also want to remain on good terms with them, as they are a reference on my current job applications, and we are also still working on papers together.

Should I refuse to submit an abstract? Or just bite the bullet and write something?
I think it can be acceptable if and only if it is clearly communicated in the submission that the former supervisor is the intended presenter.  Deliberately misrepresenting who will present at the conference is dishonest.  If in doubt, contact someone at the conference.