More than 11,000 fans packed into Singapore's indoor stadium for the event, which was the first ONE FC production to be beamed live across Asia to a potential 500 million viewers.
Aoki, who also owns the lightweight belt in Japan's DREAM organisation, took Boku to the ground repeatedly, softening him up with punches and elbows before sinking in a rear naked choke and forcing the submission early in the second round.
Bearded Boku, who beat Aoki's Evolve training partner Zorobabel Moreira at the same venue to win the title six months ago, had absolutely no answer to Aoki's superior grappling and spent most of the fight squirming on his back trying to avoid scything elbows and power punches.
"The fight went exactly to plan," Aoki said. "I won easily, but the training I went through to get here was so hard. Sparring with my training partners was scarier than the actual fight."
Aoki, who was once ranked among the world's top five lightweights and fought some of the biggest names including Gilbert Melendez and Eddie Alvarez, said he was ready to defend his ONE FC belt against anyone.
"I don't care who I fight next, I'll leave that up to my coaches, but I'll fight anyone anywhere on the planet."
Also on the card, UFC veteran Jens Pulver lost to Masakatsu Ueda by a suffocating Darce choke, while Singapore's Evolve fight team enjoyed a perfect evening with wins for Aoki, Leandro Issa, Eddie Ng, Alex Silva and Jake Butler.
Victor Cui, the CEO of Asia's biggest mixed martial arts promotion, said the event showcased how quickly the sport had grown in Asia.
"We started here in Singapore with just 7,500 fans at our first event, now we're sold out and growing from 12 events this year to 24 in 2014 all across Asia," Cui told Reuters cage-side.
"What we're particularly pleased with is our audience make up - if you look around it's all Asian faces. That means we're bringing MMA to a brand new audience and that's such a positive sign."
ONE FC's next event will be in Manila in May with local fighter Honorio Banario defending his featherweight title against South Korean Kwon Bae-young.