She played either a winger or striker and was described as a player who possesses pace comparable to that of French men's internationals Thierry Henry and Sidney Govou.

Thomis was born in the commune of Colombes, a northwestern suburb of Paris, to parents of Martiniquais heritage.

In the re-branded UEFA Women's Champions League, Thomis made eight appearances scoring three goals as Lyon reached the final in the 2009–10 edition of the competition.

In the 2010–11 edition of the Champions League, Thomis was a part of the team that won the competition defeating its nemesis Turbine Potsdam 2–0 in the final.

Competing for France in 2011 FIFA Women's World Cup and 2012 London Olympics Thomis helped the team reach the semi-finals in all three competitions.

In 2015 FIFA Women's World Cup, Thomis helped France reach the quarter-finals where the team was eliminated by Germany on penalty shootout.