The unseeded Williams was the top-ranked player in the world when she began her long layoff following her victory at the 2017 Australian Open, where she was already expecting daughter Alexis Olympia who was born in September.
After a couple of exhibitions and a Davis Cup doubles match, Williams feels she is ready to hit with the big guns on the WTA Tour again.
"I am not going to be there today or next week but I will get there and I do have my goals," Williams said.
"At some point I need to jump and fly. Every day is going to be a challenge. I know I will overcome it. It takes time to get back."
Williams entered the court Thursday night to a loud ovation, with many in the half full stadium standing and applauding as she came out of the tunnel for just her third appearance in Indian Wells in the last 17 years.
After that it was a matter of gradually asserting herself by taking control of the rallies, and she got the first break of serve in the 11th game of the first set and secured the set in the next game on her third set point.
Her daughter was born on September 1 but Williams says throughout the pre and postnatal period she tried to maintain a certain level of fitness.
The 36-year-old American is the star attraction in Indian Wells, but behind her popularity this year was the mystery surrounding her match fitness and ball-striking ability.
The 23-time Grand Slam winner answered some of those questions Thursday by blasting four aces and winning 63 percent of her first-serve points.
"From zero to Serena I am with the S," she said. "I have got a way to go.
"I wanted to stay fit just be ready. I wasn't ready to retire yet even though it would have been a great way to retire."
Williams also won an whopping 64 percent of her second serves and broke Diyas, ranked 53rd in the world, five times in the 92 minute match.
She had four double faults, but her impressive second serve win ratio was evidence of a game plan that included being aggressive and not sitting back and allowing Kazakhstan's Diyas to dictate the pace of play.
Williams set up a second round match with 29th seeded Kiki Bertens. A win over Bertens could see her face older sister Venus in the third round.
Venus, who is seeded eighth, enjoyed a first round bye and will play Romania's Sorana Cirstea in her opening match.
The birth of Williams' daughter was followed by life-threatening complications that scuppered her plans to defend her title in Melbourne.