The 28-year-old would become Hammers boss Sam Allardyce's sixth summer signing, after wrapping up a £6million deal for Stewart Downing on Tuesday.
Ba has been linked with a move away from Stamford Bridge following the return of Jose Mourinho. The Chelsea manager is said to prefer Fernando Torres and Romelu Lukaku as his options up front.
The Senegal international is of course a familiar face at Upton Park, having spent half a season there in 2010/11. However, his seven goals in 12 Premier League games were not enough to save West Ham from relegation that season.
A free transfer move to St James' Park followed, after Newcastle United exercised Ba's relegation release clause in his contract. And, after more success on Tyneside the striker earned himself a move to Chelsea in January 2013.
Last month Ba insisted that he had no desire to leave west London and would fight for his place in the Blues first-team.
But, if he is told that he doesn't feature in Mourinho's plans, then a return to West Ham might prove a favourable option before the transfer window closes on September 1.