(1) A person commits the crime of third degree criminal trespass if such person unlawfully enters or remains in or upon premises of another.
(2) Third degree criminal trespass is a class 1 petty offense, but:
(a) It is a class 3 misdemeanor if the premises have been classified by the county assessor for the county in which the land is situated as agricultural land pursuant to section 39-1-102 (1.6), C.R.S.; and
(b) It is a class 5 felony if the person trespasses on premises so classified as agricultural land with the intent to commit a felony thereon.