The 23-year-old Frenchman netted some vital goals for the Foxes last season in their run to the Championship play-off final but has only made seven appearances this term and spent a month on loan at Scunthorpe before Christmas.
N'Guessan, who moved to the Walkers Stadium from Lincoln in the summer of 2009, started his career with French side Auxerre before joining Rangers in 2005 but he failed to make a first-team appearance for the Scottish giants, spending time on loan at Boston.
N'Guessan is eligible for Southampton's FA Cup Fourth Round clash with Manchester United at St Mary's on Saturday.
Source: PA
Source: PA