That's a pretty steep punishment because it's breaking a law that says that you can't insult the royal family or mess up their things. I think tourism is fucked up, and tourists should at least have respect for places they visit by not fucking with stuff there, but fuck the thai royalty and that punishment definitely doesn't fit the "crime".
Those people shouldn't have been tourists there, and thailand needs their monarchy to be overthrown by a horizontally organized system. Maybe you can even blame the royalty for inviting all that tourism for the "damages".
Good. Fucking morons.