The tough-tackling defender was Kenny Jackett’s first signing after he succeeded Paul Cook as manager in June 2017.
Thompson arrived on a free transfer from Swindon Town, signing a two-year deal.
His current contract expires this summer, with the 27-year-old opting to shelve negotiations in February until the campaign’s closure.
Thompson has been in superb form in recent weeks, playing a key role in the Blues putting League One automatic promotion into their own hands.
He gained rave reviews for his displays in victories against Burton Albion and Coventry City over the Easter weekend.
Thompson admitted his performances were impacted on when he had a similar contract scenario at Swindon.
And he feels his decision to suspend penning a fresh deal at Pompey has been justified.
‘I think I said I was able to put it off because it affected my performances,’ said Thompson.
‘I think that by doing that I have been able to come into form now.
‘As I have previously said, when I went through contract talks last time at Swindon, it did affect my performances at the business end of the season.
‘The fact that I don’t have to worry about it and I’m letting my agent and the club deal with it in due course means I feel a lot freer.
‘I am in better form this time around.
‘It is helping me and it is helping the team, and that is ultimately exactly what I wanted to achieve.
‘I’d like to think so (his decision has been justified).’
Thompson has been Pompey’s first-choice right-back when available.
He’s made 74 appearances and scored his first and only goal in the Checkatrade Trophy triumph over Sunderland at Wembley last month.
Thompson is set to start when the two sides again battle at the Stadium of Light today.
The Chester-born talent previously told The News that he wanted to remain at Fratton Park beyond the summer.
Settled with his wife and baby boy in Stubbington, Thompson has fallen in love living on the south coast.
He added: ‘I have said constantly that I have fallen in love with the place.
‘There is no reason why (I don’t want to stay).’