No. Descartes' apprehension of his own existence as a "thinking substance" doesn't say anything about the nature of the external world.
The simulation argument is connected with Cartesian philosophy though. It is one of the possible forms of the "Cartesian demon" argument [0]. Descartes tried prove the truthfulness of experience through a twofold proof: a proof of God's existence; and a proof of His unwillingness to deceive. He does all this in Meditation III [1].
[0]: https://en.wikipedia.org/wiki/Evil_demon
[1]: https://en.wikipedia.org/wiki/Meditations_on_First_Philosoph...