No, no need to apply for 30 days tourism extension at all unless you want to. It's your choice and decision if you do border bounce at the end of the entry stamp of 60 days or apply for an extension. All people have their own priorities and criteria. Also depends on where in Thailand you would be at the end of each entry stamp.
As long as your METV is valid, you don't need to get a re-entry permit to re-enter on that visa. Multiple Entry is embedded on that visa.
you may want to check this post about METV as well.
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