[1] After completing middle school, he took a job in a candy shop to help support his family and trained as a boxer in the evening.

[3][4] Because Ohba weighed only about 105 pounds and barely stood five feet when he entered the gym, the trainers doubted that he would be successful as a professional boxer.

He trained hard, putting on the seven pounds of muscle he needed to box within the flyweight range by the time he made his debut.

Charvantchai had trouble making the weight limit, even after doing light exercise and taking a steam bath, which may have weakened him for the bout.

Chartvanchai was weakened both by a cut to his eye he received in the fourth round which gave him trouble and the efforts he took to make weight.

[11][12] On January 21, 1971, he defeated Swiss boxer Fritz Chervet in a non-title fight technical knockout at Korakuen Hall in Tokyo, Japan.

[2] His first defense was against the great champion Betulio González on April 1, 1971, in Tokyo in a very significant fifteen round Unanimous Decision.

[2] On August 19, 1971, he won a Unanimous Decision over Tony Moreno of San Antonio in a non-title ten round bout.

[14] His second defense of the World Flyweight Title was also a fifteen-round Unanimous Decision on October 23, 1971, against Filipino boxer Fernando Cabanela.

[2] His fourth WBA World Flyweight defense was against Orlando "Yango" Amores from Colón, Republic of Panamá, on June 20, 1972, in Tokyo.

He managed to pick himself up, and his corner iced his ankle in between rounds, but Ohba limped as he exchanged punches with Chionoi.

[18] Ohba was driving his new 1973 ivory Chevrolet Corvette down an expressway in Tokyo, when he hit a heavy duty eleven ton parked truck on the shoulder of the opposite lane.