Apachai is extremely tall and muscular. He has light dark skin, and is usually seen wearing a tank top and shorts with bandages wrapped around his hands and feet.
Apachai's childlike nature contradicts his deadly muay thai skills. He is very friendly with children and animals. He values the relationship he shares with Kenichi and as a result he always look our for him. Apachai often include the word 'Apa in his speech.
As a child, Apachai is brought by a crime boss to another crime boss. He tested for his strength and skills by the latter, so he easily broke the cane sent flying at him and beat up the crime boss and his bodyguards. This ticks off his own crime boss. Soon after, Apachai is bought off the crime boss by Agaard, and goes to live in the Romtyphoon gym for the next few years. Apachai would go on to look up to Agaard as his older brother.
Apachai inability to hold back is also demonstated by him razing an entire field of banana trees and knocking out his enemies in the underground ring with single clean hits, quickly becoming a fighter of his own level and making it difficult for people to match him up with others. Apachai makes a promise with Agaard that both of them will rise to the top of the Muay Thai world, and cheers on Agaard in the final round despite knowing that he will be sent to another gym if Agaard wins the match.
A few years later, after Agaard has left the Underground Muay Thai world to find a "world of true martial arts," Apachai has raised his skill in Muay Thai to the point where he blocks a robber's elbow attack with only his pinky. During this time it is also shown that the tiger cub he found has grown into an adult, named "Meo", though Apachai still thinks is just a very big cat. It is also noted that Agaard's promise to feed Apachai still takes effect, as the members of the Romtyphoon gym still put Apachai's appetite above their own based on Agaard's last request. After Apachai returns to his gym, Agaard assaults him to test his strength, becomes disappointed in Apachai's delayed training, and advices Apachai to join "Yami". This prompts Apachai to set out on his own journey to find his own way.
Apachai goes on his journey, but quickly starves and does not have access to much food. He eats the hamburger that Hexford drops for him and pays him back with his services as a bodyguard. However, he remains unaware of the true nature of his employers, and starts a fight with the invading elder, who matches him strike for strike and continues to fight while dodging bullets. Apachai becomes disillusioned with the child traffickers when he realizes their true nature and takes out his employers, frees the children, and brings the treasure from the ship to finance the poor village. He follows the elder and Miu until they return home to Ryozanpaku, after which he becomes a part of the extended family of masters.
As one of Kenichi's masters, Apachai trains with Kenichi on mulitiple occasions, often knocking him out unintentionally and making Kenichi fear him for his lack of ability to hold back. Being saddened by this fact, Apachai learns how to hold back his strength through his own training with the elder and manages to teach Kenichi the Khao Loy. Apachai still has not refined the ability to hold back though, and occasionally still knocks out Kenichi when he enters his fighting mode.
In the YOMI arc, Apachai tells the Elder that he knows one of the members in Yami, (speaking of Agaard). Apacahi would finally get his destined match against Agaard. During the fact it was agreed that Agaard would win if he kills Apachai while Apachai would win without killing Agaard. Later on in Chapter 400, during his fight with Agaard, Apachai becomes critically injured by a punch that pierced the left side of his stomach, though he manages to strike a blow of his own before he fell, injuring Agaard to the point where the latter falls as well and is unable to move for the next 48 hours. As a result Apachai and Agaard fight ended in a draw. It has been confirmed by both Agaard and the Bantou master that he was dead, though both of them were heavily injured when they tried to confirm this and he becomes "revived" by his resolution to protect Kenichi against the Bantou master. Despite his mortal wound, Apachai defeats the Bantou master in single punch, launching him out of the building. Relieved that Kenichi is safe, Apachai feels the rest of his strength leave him. Just as Apachai begins to submit to his wounds, feeling his time is up, Akisame and Kensei arrive, and quickly begin surgery to save his life.
Apachai is nicknamed the Death God of the Muay Thai Underworld. He is the Muay Thai expert of Ryozanpaku. He is regarded as one of the finest Muay Thai practioners that has ever lived.