Did in a joint trip with Marapi. Started from the latter's top in the morning and made it to Singgalang's by evening the same day. Amazing lake up there where the crater used to be. Climbed one of the telecommunication masts up the top. Great views from there.

Full trip report + map:
http://dimitriosfan.com/2016/06/30/from-mount-merapi-to-mount-singgalang/