the mystery is why people who speak English are unable to figure out what "arrival" means. They ask do they have to fill in an arrival card if arriving in thailand. Or those who want to extend their stay and say they want to renew a visa.
then if you have a valid visa you can extend by 30 days. And if eligible based on passport you can leave and "border bounce" for an entry with no visa. But you didn't say what passport you have.