The 19-year-old has been the subject of interest throughout the summer after an excellent breakthrough season in the Easter Road first-team saw him help the club reach the latter stages of both cup competitions and finish third in the league.
Watford had an offer of around £2.5 million for the player rejected earlier this summer. The EPL newboys have since recruited former Tottenham Hotspur and England left-back Danny Rose and are not expected to return with an improved offer for Doig this summer.
The Athletic reports that West Ham and Championship side Forest have now joined the chase. AC Milan and Arsenal have also been credited with an interest.
Hibs are said to be demanding £5 million for the young Scot after managing to get him signed to a long-term contract in February.
Hearts exit on the cards for Josh Ginnelly
Lee Johnson addresses Hearts claims that Hibs over-celebrated derby equaliser
Steve Kean reaction as Hibs B bow out of SPFL Trust Trophy and Paul Hanlon gets minutes under his belt
Hearts B come up short against Buckie Thistle in SPFL Trust Trophy
Lee Johnson open to more transfers but says Hibs have gone over budget after Martin Boyle arrival