The ex-Prez spoke to the media anew Friday at Trump Tower in NYC -- his first official press conference since he got convicted Thursday on 34 felony counts of falsifying business records ... something he says was absolutely ridiculous, with the deck stacked against him.

DT rattled off what he thinks he did in terms of Michael Cohen and Stormy Daniels -- characterizing the alleged hush money payment as nothing more than a standard business expense that was on the up and up -- and went on to slam the judge ... while also laying the blame for this case being brought at Biden's feet.

Trump also decried the fact he was under a gag order -- something he was found to have violated, for which he was fined thousands of dollars -- and he scoffed at the notion he was being threatened with jail. Even now, he faces years behind bars ... which he finds ridiculous.

Interestingly, Trump also says he was all gung-ho on testifying on his own behalf ... something he says he was ultimately advised against by his lawyers -- out of fear of getting dinged for technically saying something wrong and getting found guilty of perjury.

Trump says this whole thing was nothing but a political witch hunt -- and went on to give a stump speech of sorts ... listing problems he sees with the country. Same old, same old.

The guy is the first U.S. president to ever become a convicted felon ... and yet, he's more fired up than ever -- as are his loyal supporters, who were up in arms over the conviction. Time will tell if this ends up helping or hurting him ... and what his sentence will be.