There isn’t an any way to do it with SmartThings itself for the reasons that @marktheknife mentioned, but there are some plugs which are used to control modems which know when they themselves lose connection with the Internet and are used to reboot modems. That might solve your problem.
There are several different brands of these, here’s one just as an example:
And another one:
And another one in case you want to shop at Amazon:
And Ankuoo offers a very stripped-down single socket version for under $20
All the brands work about the same way, they just have a site that they ping frequently and if the ping doesn’t go through, the pocket socket re-boots itself. Read the product specs carefully as they do have somewhat different features. For example, the first one I listed lets you plug two devices into it and also lets you pick which sites to ping. 