With just four games remaining, including one looming against their nearest rivals Swansea, Southampton sits four points away from safety but has just one league win in 2018.
Despite a good showing at Chelsea before their second-half collapse on Saturday, Southampton reverted to looking void of any creativity and again lacked an end product.
Shane Long came closest to a goal for the visitors, but was denied from point-blank by Ben Hamer who had little work through the match.
Southampton withstood a trio of half chances from Leicester in the opening 45 minutes, which was largely uneventful.
Riyad Mahrez squibbed a shot into the grasp of Alex McCarthy, Kelechi Iheanacho fired narrowly wide of the post and Wilfred Ndidi drew a fierce save.
Long was closest to etching his footprint in what could’ve been the start of a great escape for Saints, but Hamer kept out the chance on 57 minutes.
The striker, who was just outside the six yard box, swivelled and hit an effort on target that was punched aside.
Leicester consistently made better use of their possession throughout, though likewise struggled for an end product.
The hosts, however, nearly took a surprise lead 20 minutes from time, but McCarthy tipped Jamie Vardy’s effort over the bar after the forward latched onto a long pass over the defence.
Southampton would be left disappointed at the full-time whistle as chances to protect their status dwindle.
Leicester: Hamer, Dragovic, Maguire, Chilwell, Albrighton, Ndidi, Silva (Barnes 90+1), Mahrez, Gray (Choudhury 90+1), Iheanacho (Diabate 76), Vardy (c).
Unused subs: Jakupovic (GK), Simpson, Fuchs, Morgan.
Southampton: McCarthy, Bertrand (c), Bednarek, Yoshida, Hoedt, Romeu, Hojbjerg (Redmond 88), Ward-Prowse (Davis 58), Tadic, Long (Austin 73)
Unused subs: Forster (GK), Pied, Sims, Gabbiadini.