Jeff Bezos just added BILLIONS to his massive fortune -- which is nothing new for him, but what's new this time ... it only took a few strokes of the clock to make that increase.

Stock for the Amazon honcho's company surged 12 percent in a matter of 15 minutes Thursday afternoon, which equaled an astounding 11-digit increase to his bottom line.

The astronomical math? Bloomberg says Jeff added $13.2 BILLION just from the surge, which raises his net worth to about $129.5 billion. Forbes was a wee bit more modest, reporting Bezos added $12.8 billion to his portfolio, with a new net worth of $128.9 billion.

Either way ... ya get the point. Bill Gates feels like a panhandler right now.