US will use all manner of tools to extradite foreign citizens who have never been to the US because they broke US law.
Nobody has to worry about breaking Thai laws around defaming the King because Thailand isn’t a superpower with the ability to enforce its will beyond its borders.
Except what you wrote only applies to countries with extradition treaties with the US (meaning the government in those countries have agreed that US law can apply in their country too).
Not every country has this, so no, not "everyone has to be worried about breaking US law".
Regarding Thailand specifically, they have a principle of "double criminality", so people are only extraditable if what they're accused of is a crime both in Thailand and the country they're being extradited to. So maybe not the best example.
Besides, other countries have extradition treaties with other countries than the US too, even non-super power ones.