Loan Watch: Britt scores again for Shrimpers
The DR Congo-born attacker grabbed his second goal for the Shrimpers, the winner against Thompson's Chairboys.
Assombalonga has now made four appearances for Paul Sturrock's side, notching his first goal for the Essex club in the 3-3 draw with Aidy Boothroyd's Northampton Town the previous Saturday.
Thompson was of course on the losing side as he made his debut for the Buckinghamshire side.
Elsewhere in League Two, Dale Bennett made his debut for Wimbledon having joined the Wombles on-loan on Transfer Deadline Day.
The 22 year-old centre-back played the full 90 minutes for Terry Brown's side, who drew two apiece with Dagenham and Redbridge.
Goals from Jack Midson and Byron Harrison cancelled out strikes from the Daggers' pair Michael Spillane and Luke Howell.