After winning titles in Brisbane, Abu Dhabi and Stuttgart, former Wimbledon champion Rybakina, who is among the title favourites at Roland Garros alongside Iga Swiatek and Aryna Sabalenka, had to pull out of the Italian Open due to illness.
The Kazakh was also forced to withdraw from the French Open last year due to illness, but after a dominant first-round win over Belgium's Greet Minnen, Rybakina said she is good to go at the clay-court slam and appeared irked by questions about her fitness.
"I feel quite confident," Rybakina told reporters after her win on Tuesday.
"For sure, physically I'm much better than last year since I had to withdraw. I had COVID-19, so of course, now I'm much better. The questions are quite the same, so I don't know what to say anymore.
"(Longer tournaments) are tiring sometimes, but I mean, now I'm happy to be back and just to keep on playing. Then the goal is for me to win the titles. That's what I want. That's what I'm aiming for."
Rybakina next faces Dutchwoman Arantxa Rus, who she beat when the two last met at Roland Garros in 2022, and is on course for a potential semi-final meeting with Australian Open winner Sabalenka, who also plays on Thursday.
Sabalenka began her Roland Garros campaign by dismissing Russian Erika Andreeva in a dominant 6-1, 6-2 first-round display and continues her quest to dethrone three-times champion Swiatek when she takes on Japanese qualifier Moyuka Uchijima.
In the men's draw, world number one Novak Djokovic continues his title defence against Roberto Carballes Baena, while last year's losing finalist Casper Ruud also faces a Spaniard in Alejandro Davidovich Fokina.
Norwegian Ruud said he was high on confidence after winning the Geneva Open last week, adding: "That's why I like playing (the week before a Grand Slam).
"It gives me confidence and match feeling going into a Grand Slam, which is the Grand Slam that I personally feel like I have the most chances to do well in."
Fourth seed Alexander Zverev, who beat 14-time winner Rafa Nadal in the first round, takes on David Goffin while fellow top-10 seed Daniil Medvedev faces Serbian Miomir Kecmanovic.