Last year he released a satirical song, and music video by Jeremy Jones, titled Planet Key, which pictured the Prime Minister strumming an endangered Maui's dolphin while an oil rig explodes in the background.
The Electoral Commission banned television and radio broadcasts of the song, decreeing it a breach of the Electoral Act. Watson and Jones challenged the commission in court, saying their work was intended only to lampoon.
On Saturday, he took another tuneful "dig at the big boss" in a song played on the steps of Parliament at a rally protesting the TPPA.
"It's up to every musician and artist as to where they draw the line, but for me politics is part of life. Everything you do is political.
"You've got to fight against these big PR machines and it's not just me. New Zealand has a history of it going back to the 80s when I was [a] teenager. There was a lot of political music at the time and a lot was happening. It was a time of change and things feel the same now."
But his set list for King Street Live will cast only a shadow of the body politic at best, he said.
"I'll keep the old politics in there but this gig in Masterton will be really just about a good time, you know. I might play one of those songs but I'm not going to be preaching," he said.
"I just love playing for people, solo or with a band, and the past ten years of my career has been awesome. My whole life is music today. I'm blessed and I just want to keep sharing that for as long as people want to keep listening."
Tickets are available for the Blues in the Night show at King Street Live on Saturday for $21.50 each at upwithpeople.co.nz and eventfinder.co.nz
