A loony part-time chef — who once robbed a bank dressed in his mom’s clothes — strangled his Long Island neighbor and then nearly decapitated the corpse before stuffing it in his bedroom closet, cops said yesterday.

Crazy ex-con Aston Barth, 33, of Central Islip, continued to live with his victim’s body for nearly a week before his mother and brother discovered it Christmas Eve, cops said. Sean Epps said he had repeatedly gone to Barth’s home last week to ask if he had seen their mutual pal, victim Jason Campbell. “The whole time, my friend was in the closet right there,” a stunned Epps saidaid yesterday as he set up a makeshift memorial near Campbell’s home.

“I don’t know how you can just stay in there with a body in your bedroom for a week — I didn’t think Aston could do something like this,’’ said another Campbell pal, who only gave her first name, Marquise.

Barth — who drew national ridicule in 2007 after robbing a Central Islip bank dressed like a lady despite his thick black mustache — admitted to fatally choking Jason Campbell, a longtime pal, during an argument, authorities said.

It wasn’t clear what the pair fought about, but after Barth killed his 35-year-old pal, he tried to decapitate and dismember him with an ax, officials said.

Barth only got through one whack, on the neck, before he realized it was too much work and simply put a black garbage bag over Campbell’s head, wrapped him in a blanket and stuffed him in the closet, authorities said.

Barth had just been released from prison for the bank robbery in September and returned to live with his mother, Connie, and a younger brother.

Connie Barth said her son has been mentally ill since childhood, when he used to behead animals for fun.