"There has been an interest from Middlesbrough," said Smith. "So far we haven't reached any agreement."
Smith had made a new contract for the 25-year-old a priority but the club may now be willing to part with Thomson.
Thomson, capped twice for Scotland signed from Hibernian in January 2007 on a four-and-a-half-year deal.
He has suffered two serious knee injuries in his career, the most recent being in November 2008, but on each occasion Thomson has fought his way back to full fitness and first-team football.
And he was a near ever-present last season as Rangers picked up a league and Co-operative Insurance Cup double.
Smith has seen top scorer Kris Boyd leave under freedom of contract, along with Nacho Novo, DaMarcus Beasley and Steven Smith.
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And despite negotiating a more favourable budget with Lloyds Banking Group, the debt-laden Scottish champions admit they are susceptible to bids for their top performers.
Algeria defender Madjid Bougherra has been the subject of increased speculation following his World Cup exploits but there is no imminent sign of a move.
"We had an enquiry from Hamburg about a month ago but they haven't followed that up," said Smith as he helped launch an initiative to provide members of the Armed Forces with free tickets.
"He is coming back to us at the weekend following his World Cup campaign.
"We've had no other enquiries for any of our players and I hope it stays that way.
"We've got a group of about 18 at the present moment, we'd obviously like to add a couple of players to that and then we've got some younger players. We would maybe like to see a couple of players come in in the next few weeks.
"We're solid enough at the back. It's maybe the wider areas of the pitch, the midfield areas where we need to add to and that's where we'll be looking over the next few weeks.
"Kris was terrific for us in terms of the number of goals that he brought to the team but goalscorers are not easy to come by and they're normally not cheap either. It'll be difficult for us to fill that gap but it's one of the challenges we face this season."
And, asked if money generated from player sales would be reinvested in the squad, Smith replied: "A percentage of it would. That's where we stand."
Source: BBC Sport
Source: BBC Sport