From the stickied post on Ubuntu forums:

"The buttons are in the old location on all default themes apart from
Ambiance,Radiance and Dust, If you still want the Ambiance ,Radiance or Dust
theme but with buttons on the right, choose one of those other themes and
use the Customize button to achieve what you want. e.g.
1. System > Preferences > Appearance
2. Select the theme icon "New Wave"
3. Click the button "Customize.."
4. Select tab "Controls" and select "Ambiance"
5. Select tab "Window border" and select "Ambiance"
6. Select tab "Icons" and scroll down and select "Ubuntu-mono-dark"
7. Select "Save Theme" to your choice.
*Using gconf-editor is not the right approach as this could bork future
themes. This change makes it easier for themes to do interesting things with
window borders. Unfortunately, if the wrong approach spreads, they won't be
able to do that.*

ohioloco.ubuntuforums.org/showthread.php?t=1469475