The Frenchman has been heavily linked with a move back to his homeland this summer with Andre Villas-Boas keen on the player.
The Portuguese manager has taken over at Marseille who are rebuilding this summer after a fifth-place finish in Ligue 1.
Sales are required before they can start buying with the club in talks with West Ham United over the transfer of Morgan Sanson for £30million, according to the Daily Record.
The 24-year-old could be joined by another midfielder through the exit door with OM keen to get Dutch international Kevin Strootman off the wage bill.
The former Champions League winners face competition from Porto for Ntcham with Celtic quoting between £13million and £15million for the French U21 international.
He was bought for £4.5million from Manchester City in the summer of 2017.
Ntcham gave a hint that he was departing Celtic when he reportedly unfollowed his team-mates on Instagram.