What is called an intentional thought?
There's no sin in Buddhism. Buddha will not be offended if you're thinking some silly thoughts. Don't hurt yourself with this fear. No need to perpetuate those silly thoughts either, it won't do you any good. Focus on what's beneficial. Such as study of Dharma.
Karma is not watching you, it does not revenge or punish. Karma is the future you build with your choices, day after day after day.