Poker Star Phil Laak -- Tax Man Calls His Bluff -- Ante Up...Or Else

Card shark Phil Laak -- who's made millions on the pro poker circuit -- just got dealt a lousy hand ... against an opponent who almost never loses-- the Tax Man ... TMZ has learned.

The Unabomber (it's because of his hoodies and sunglasses) was hit with liens for unpaid California taxes in 2010 and 2011 ... according to docs filed by the state tax board.

The docs show Laak owes a total of $24,874 in taxes for the 2 years -- a pretty small stack for Laak, who's earned almost $3 million dollars on the tournament circuit ... including a $263K purse at the 2010 World Series of Poker in Europe.

Gotta know when to fold 'em.