my first and foremost advise, seek the help and advice of a lawyer on this one and prepare all the legal documents (certificate of title, property tax receipts (amilyar) etc.) that will prove your ownership of your land.
anyways in my appreciation of your case, you can have the following actions:
if you are contemplating a civil case:
1. if it is still within one year from the time they actually and unlawfully took possession of your land, go to the MTC or MeTC of the place where your land is located and file a case of forcible entry with damages and a prayer for a writ of preliminary injunction and temporary restraining order to stop them from engaging fruitfully from your land.
2. if it is more than a year but not exceeding 10 years (i deemed that there is an implied or cosntructive trust because it was initially occupied by a family member, who is now deceased, of yours, go to the RTC of the place where your land is located and file a case of accion reinvidicatoria with damages and a prayer for a writ of preliminary injunction and temporary retraining order to stop them from engaging fruitfully form your land.
if you are contemplating a criminal case:
you may file a case of trespass to fenced estate or closed premises (trespass to property) before the MTC or MeTC, provided the following requisites must be present:
1). The estate or closed premises must be uninhabited (walang nakatira);
2). There is a manifest prohibition against entry, such as a sign, or perimeter fence even if only a strand of barbed wire; (dapat may bakod ang property mo) and
3). The permission of the owner or caretaker has not been secured. (obviously you did not permit them to occupy your property)
also, base on your story it appears to me that you do not dwell or live on your property so a criminal case of trespass to dwelling is not applicable in your case.
good luck.