He's HUGE....

"General" Larry Platt is finally cashing in on his "Pants on the Ground" phenomenon -- because "American Idol's" favorite senior citizen is now getting paid to play in Las Vegas.

Platt is scheduled to perform his semi-hit at JET nightclub at the Mirage Hotel today.

Sources at the hotel say Platt is being flown from Atlanta first class ... and will get pampered with free food, lodging, several thousand dollars and, last but not least, a steak dinner!