This is a common mistake in English. Since the comparative form of an adjective is formed by simply sticking “er” to the end of an adjective (apart from a few irregular adjectives like “good/better”), learners and native speakers alike sometimes think that when something is “more free”, it should be “freeer”. The truth is that there is not a single word in English whose standard spelling would contain “eee”. The simple rule is:
For example, “most free” would be “freest”, not “freeest”. Note, however, that “freest” is pronounced as if it were written as “freeest”, i.e. /friːɪst/. The same goes for “freer”, pronounced as /ˈfriːə(r)/. “Free” is in fact the only adjective ending in “ee”, apart from compound words formed from it, e.g. “carefree” which are not comparable, so there are no words like “carefreer”.
The “er” suffix can be added also to verbs, where it expresses the person who does the action. For example, someone who skies (/skiːz/, from the verb “to ski”, not /skaɪz/, the plural of “sky”) is a “skier” /ˈskiːə(r)/. In the same vein, someone who sees (the future) is a “seer”, not a “seeer”, in accordance with the rule above.
The pronunciation in this case is slightly more complicated. In British English, it is /siːə/, i.e. exactly like “see” + “er”. In American English, however, it is pronounced as it is written, that is /siːr/, without /ə/.