should i send originals or copies of documents like, bank statements, passport, lease agreements, etc etc for a tourist visa or do they have to be the originals?

What country are you applying for a visa for?

Most countries ask for original documents, because they can be faked, which will be returned, and copies of some documents.

Obviously the original passport must be submitted, that's where the visa will be put, in the event of a UK sponsored application a copy of the sponsors passport. Bank statements, originals and copies.

This is the list from the UK which indicates originals and copies of some documents, http://www.vfs-uk-th.com/images/VisitSocial.pdf but as I say it depends on the country you are are applying for.