It depends of you country of origin if you can apply for an extension.
If you arrived with visa exempt, you can apply 30 day extension in the immigration. If you arrived with visa on arrival, it usually cannot be extended.
If you have an accident your insurance does not cover anything if you dont have a proper license. Lots of accidents every day because tourists rent motorbikes and cannot drive.
Visa is applied outside of the country, extension of stay is applied in immigration inside the country. If you arrived without applying a visa, you have 30 day visa exeption which you can extent for 30 days at your local immigration office.