All types of tourist & visit visas can be extended for 30 days twice, upon applying for it and after successful approval. This visa can be done without the need to leave the country.
Visitors and tourists can apply for the second renewal before the expiry of the first one against paying the fees each time of renewal.
Visa overstayers who do not renew, as above, will have to pay fine for each day of their overstay.
There is an exception to some of the tourists in UAE. They are not obliged to follow the rule for the extension that others need to abide by.