Midfielder Thompson, 29, has made only one Premiership start since joining Pompey on a year-long deal in July 2006 from Wigan.
He said: "I spoke to the manager to tell him I was frustrated. But I am not looking to leave the club."
Thompson is an all-action midfielder and product of Liverpool's youth system and he spent the previous six months at Wigan after being released by Blackburn.
He had made a return to the Premier League when joining Rovers from Coventry City in 2002, where he was voted player of the season in 2001/02.
Thompson netted on his Latics debut against Middlesbrough in January 2006.