Edward Furlong -- Back Behind Bars

It's a pity the L.A. County Jail system doesn't have a rewards program ... because "Terminator 2" star Edward Furlong has just checked in for the billionth time.

You'll recall, Furlong was arrested last month for allegedly violating a restraining order obtained by his ex-GF, whom he allegedly roughed up on multiple occasions. Furlong was subsequently released on $50,000 bail.

But yesterday -- when Furlong was back in court -- the judge decided his previous bail amount wasn't enough ... and raised it to $100,000 ... at which point Furlong was taken back into custody.