бейса

Що это значит?

"Хоть об стенку бейса дни и ночи, ты не вернешь промчавшиеся дни"

it's бейся with a mistake in it.
"You could hit a wall(throw yourself to a wall) days and nights but you won't return days that are gone"

Хоть головой об стену (стенку) бейся

The verb suffix -ся is normally pronounced like [са] after т or ть only:
биться [б’и́тса] (hard [с]), but бейся [б’е́йс’а] (soft [с’]).
Though in Old Moscow dialect, it is always pronounced like [са] (and -сь like [с]).
For instance, Vladimir Vysotsky had this feature in his pronunciation. So the word парус rhymes with каюсь in his song:
Владимир Высоцкий - Парус - YouTube or Высоцкий - Парус.mp4 - YouTube