Thilo Kehrer diverted Harry Kane's low cross into his own goal in the 34th minute after unbeaten Tottenham had also had a penalty overturned by a VAR check.
West Ham responded well though and Tottenham could have no complaints at having to settle for a draw.
Soucek thumped home a close-range finish in the 55th minute after which both sides could have snatched a winner with West Ham going closest in stoppage time.
Third-placed Tottenham have 11 points from their opening five games, four behind leaders Arsenal.
West Ham, who got their first win of the season at the weekend, are in 14th place with four points.