Neither side were really in the first period, but Charlie Austin's strike saw the Saints ahead. Claude Puel's side controlled the proceedings in the second period, and proved decisive with goals from Dusan Tadic and James Ward-Prowse securing an easy three points.
Out of nothing
Slaven Bilic's side were looking to avoid a fourth consecutive league defeat, however as the match kicked-off both sides lacked any real integrity to grab the game.
The Hammers had a penalty shout as Cedric Soares flew in on Simone Zaza, despite the pressure of Jose Fonte, but Jonathan Moss waved the appeals away.
The sides looked to be heading into the break goalless, however out of nothing the away side managed to take the lead.
The blame could fall at the door of Adrian as the ball was played to Ryan Bertand who was running into the area, he found Austin whose effort went beyond the Spanish 'keeper and into the net.
It could of easily been two in quick succession. Tadic played a great ball in from the flank for Soares, but his effort could only find the side-netting.
Under the quash
It didn't get any better for the Hammers in the second period, with Saints pretty much dominating the proceedings.
Adrain made up for his earlier howler, producing a good save from Fonte's header and then getting down to palm away Tadic's low effort.
However there is nothing he could do to prevent the Serbian from doubling Southampton's second just after the hour mark.
This time Chiekhou Kouyate was dispossessed in the middle with Austin finding Tadic. He kept a cool head to round the onrushing Adrian and tap it coolly into an empty net.
Running out of luck
It was turning into another embarrassing day for the Stratford side, and it was clear to many that it wasn't going to be their day late into the contest.
The home side continued to appeal for spot-kicks on Zaza, then it was then the turn of Dimitri Payet whose effort hit the arm of Bertrand, but was again waved away.
They went close to getting one back in the 78th minute, with Fraser Forster's punch landing at the feet of Zaza, but his effort was just cleared off the line by Virgil van Dijk.
Another bad day at the office
West Ham looked dead and buried as the game entered it's dying moments, but the Saints made sure of that with the third and final goal.
Nathan Redmond started the move, finding Steven Davis who had made a great run into area, he squared to substitute Ward-Prowse and knocked home to cap off another miserable day for the West Ham faithful.