Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
The majority of scholars are of the opinion that the person who gives up praying out of laziness is Fassiq (dissolute) who commits a major sin. But he is not considered Kafir. So, he is to be washed, shrouded and prayed on. He should also be buried in the graveyard of Muslims. There is no Hadith – to our knowledge – that prohibits performing funeral prayer on a Muslim who dies while giving up prayer.
The Hambali, however, are of the opinion that the person who gives up prayer out of laziness is considered Kafir if he refuses to repent after the Imam told him to do so and provided he refuses after three days of warning to repent and keeps on his refusal to pray. He should then be killed and Muslims do not pray on him.
Allah knows best.