Ba shared a picture with several Chelsea stars, Big Ben and ‘Champions 2014-15’ written in the background.
The former Blues striker also added the following caption: “Congrats to my former club @chelseafc and team mates for the title and the great season. On top of the table from the first to the last day.”
The Senegalese international scored six times in 22 matches under Rafael Benitez for Chelsea and then eight goals in 29 games under Jose Mourinho.
Ba was involved in Chelsea’s title race last season, the Blues finished the Premier League in third place, four points behind 2013-14 champions Manchester City.
The powerful striker joined the Black Eagles from Chelsea this summer and already has a total of 25 goals and seven assists for Beşiktaş.
Ba also recetly invited former teammates Chelsea captain John Terry and winger Eden Hazard to a charity dinner on 25 May 2015.
The charitable event will raise funds for the orphans of Senegal and take place in central London.