Correct spelling


Correct spelling, explanation: the correct form, these, comes from Old English pronouns thes or theōs, and the spelling probably origins in them. The confusion with wrong form theese may derive from the pronunciation of these. As a determiner, the word is pronounced with a shorter sound /i/, however in its more often use, as a pronoun, it is pronounced with a long /i:/ sound: /ðiːz/ [theez].

Definition of these:
1. pronoun, plural of this
These are my children.
These flowers are dead, throw them away!
2. determiner, to talk about things mentioned before; in the spoken language used to introduce something in a story
I would like to visit some Mediterranean countries this summer. These countries are sunny and have the best food.
Then, these guys came in and wanted to fight, could you believe it?

Incorrect spelling


Incorrect spelling, explanation: theese is an incorrect form because this pronoun is spelled with just one vowel e in the middle. It originates in the Old English spelling of plural pronouns (thes masculine and theōs feminine). Therefore these is the correct form.