Press Association Sport understands the 25-year-old was heading for Teesside for talks on Tuesday after the clubs agreed a deal.
Thomson would become the latest recruit from Scotland, with Strachan having already signed Celtic old boys Barry Robson, Chris Killen, Willo Flood and Scott McDonald, former Rangers striker Kris Boyd and Lee Miller from Aberdeen, while Celtic defender Stephen McManus, who spent the second half of last season on loan at the Riverside Stadium, remains very much on his radar.
Once-capped Scotland international Thomson, who has a year left on his contract at Ibrox, is valued at around ¦pound;2million.
Source: PA
Source: PA