In short, I would say that Service Design and Design Thinking have more similarities than differences.

Here an excrept from my course "What is Service Design" that covers this question in more depth:

In 2016, I was invited to cover The Global Service Design Conference as a blogger. There was a debate about Service Design and other disciplines. In the middle of this debate, which looked a lot like a tiny religion war, I came up with this little comic strip.

For me, this one describes pretty well how I view these different fields. They all have their own fancy identity; but, in the end, they all care about one thing: they want to make people happier. If you absolutely want to call it Experience Design over Service Designers, that’s totally fine by me.

I'd recommend you read the chapter "Where does Service Design come from?" from my free course "What is Service Design" to know even more or check this conversation on the Service Design co-creator community. To have access to it, you first need to join the community for free here.

In this 7-minutes video Marc Fonteijn gives his take on this question.

Check out all the questions about the differences and complements between Service Design and other fields.