The 33-year-old, who was once regarded as the best player in the world, has not played for his country since featuring against Chile in April.
However, the former Barcelona playmaker believes that his relationship with head coach Luiz Felipe Scolari could help him secure a spot.
"He is a very direct person and is always open with me. I know that there are still opportunities available for those who are playing well," Ronaldinho told FIFA's official website.
"He seems to have the core of his squad decided but whoever is in good form at the right time will go too. I'm always working hard to improve. If there is a chance of playing in the World Cup, I'll be ready and I'll be at my peak. My goal is to always be at my best.
"It was great to be back with the national squad [earlier this year]. Luiz Felipe Scolari and I have won so much together and we have a good relationship."
Ronaldinho has made 97 appearances for his country, scoring 33 goals in the process.