Son opened the scoring in the first half and Dejan Kulusevski doubled the lead early in the second half, with the South Korea international scoring twice more after the break.
The win takes Antonio Conte's team to 57 points, three points clear of fifth-placed Arsenal and six clear of West Ham and Manchester United. A few weeks ago Tottenham looked long shots to qualify for next season's Champions League but a run of six wins in seven Premier League matches has transformed their season.
Spurs were in front at Villa Park in just the third minute when Son lashed a first-time effort into the bottom corner after Harry Kane's shot was blocked. That proved to be the only goal of the first period, though Villa were a regular threat.