If your original tourist visa has expired (visa on arrival), you can re-apply for a new visa for 30, 60 or 90 days.
If you originally had a free "visa on arrival" and it has expired, you can apply for a new paid tourist visa to continue your stay in the UAE.
To apply for a new tourist visa, you need to leave the UAE, get a new visa, and only then check in.
Alternatively, if you plan to stay in the UAE for a long time, it is better to apply for an Emirates ID (resident visa).