Issei Ishii

Ishii faced the one-time Lumpinee Stadium flyweight title challenger Kazuki Osaki for the inaugural KNOCK OUT Flyweight championship at KING OF KNOCK OUT 2018 on December 9, 2018. He won the fight by majority decision, with all three judges scoring the bout 49–48 in his favor.[1]

Ishii faced Yoddoy Kaewsamrit for the WPMF World Flyweight championship in his next fight, at KODO 4 on February 24, 2019.[2] He won the fight by a third-round technical knockout.

After capturing the KNOCK OUT and WPMF titles, Ishii fought Petchthailand Moopingaroijung for the vacant IBF Muay Thai World Flyweight title at the June 12, 2019 Suk Wan Kingthong event. He won the fight by a third-round knockout, stopping Petchthailand with a spinning backfist at the very end of the round.[3] Petchthailand and Ishii fought an immediate rematch at the August 9, 2019 True4U event, with the WBC Muay Thai World Super Flyweight title on the line. Ishii lost the fight by decision, with scores of 48–49, 47–49 and 47–50.[4]

Ishii faced Nuapetch KelaSport in a non-title bout at the November 13, 2019 Suk Wan Kingthong event. He won the fight by third-round technical knockout.[5]

Ishii was booked to face Hiroyuki for the Battle of Muay Thai Super Flyweight title at BOM WAVE 01 ~ Get Over The COVID-19 on June 28, 2020. He won the fight by unanimous decision, with two judges scoring the bout 49–47 in his favor, while the third judge scored the bout 50–47 in his favor.[6]

Ishii faced Yuya Iwanami in a non-title bout at NO KICK NO LIFE ~Shin Shou~ Diamond FES on October 29, 2020. He won his promotional debut by a second-round technical knockout, after he forced Iwanami's corner to throw in the towel.[7]

Ishii made his first BoM Super Flyweight title defense against Satoshi Katashima at BOM WAVE 01 ~ Get Over The COVID-19 on December 6, 2020. Aside from Ishii's title, the WPMF World Super Flyweight title was on the line as well. Ishii won the fight by unanimous decision, with scores of 50–46, 49–48 and 49–47.[8]

Ishii faced Reiya in a non-title bout at NO KICK NO LIFE ~Shin Shou~ Ungaisouten on February 24, 2021. He won the fight by unanimous decision, with all three judges awarding him a 30–28 scorecard.[9][10] Ishii faced Sanchai TeppenGym in another non-title bout at BOM WAVE 04 – Get Over The COVID-19 on April 11, 2021. He won the fight by a fourth-round knockout.[11]

Ishii was booked to face Kazuki Osaki at RISE WORLD SERIES 2021 on July 18, 2021, in the semifinals of the 2021 RISE Dead or Alive super flyweight tournament. The winner of the tournament was expected to face Tenshin Nasukawa in his final bout with the promotion.[12] Ishii lost his RISE debut by unanimous decision, with scores of 29-28, 29-28 and 29-27.[13]

Ishii returned to Battle of Muaythai for his next fight, a non-title bout against Kojima Nor.Naksin at BOM WAVE 06 – Get Over The COVID-19 on November 7, 2021. He won the fight by unanimous decision, with all three judges scoring it 49–48 for Ishii.[14]

On January 9, 2021 Ishii faced Ryu Hanaoka at the NO KICK NO LIFE event. He lost by unanimous decision after five rounds.[15]

Ishii faced Khun Namisan Shobukai at BOM WAVE 08 – Get Over The COVID-19 on April 24, 2022, in his final fight with the promotion before signing with K-1. He won the fight by a second-round knockout.[16]

On June 14, 2022, it was revealed that Ishii had signed with K-1. He was booked to make his promotional debut against Kazuki Fujita at K-1 World GP 2022 in Fukuoka on August 11, 2022.[17] Ishii won the fight by a third-round knockout, flooring Fujita with a right straight at the 2:41 minute mark of the round.[18]

Ishii faced Detchphet Wor.Sangprapai for the vacant WBC MuayThai World Super Flyweight title at The Battle of Muay Thai "OUROBOROS" on September 23, 2022.[19] He won the fight by knockout in the first round with a series of left hooks.[20]

Ishii faced the undefeated WKA World -54 kg champion Oscar Bohorquez in the quarterfinals of the 2022 K-1 Bantamweight World Grand Prix. The one-day tournament, held to crown the inaugural K-1 bantamweight champion, was held at K-1 World GP 2022 in Osaka on December 3, 2022.[21] He forced a referee stoppage with a flurry of punches with 13 seconds left in the second round and advanced to the semifinals, where he faced the reigning Krush Bantamweight champion Koji Ikeda.[22] Ishii won the fight by unanimous decision, with scores of 30–29, 30–29 and 30–28. He advanced to the finals, where he faced the 2021 K-1 Japan Grand Prix winner Toma Kuroda.[23] He lost the fight by split decision, after an extra fourth round was contested.[24]

Ishii faced Yodsila Chor.Hapayak at K-1 World GP 2023: K'Festa 6 on March 12, 2023.[25]

• 2010 WINDY Super Fight -30kg Champion
• 2010 M-1 -35kg Champion
• 2010 King of Strikers -35kg Champion
• 2011 Windy Super Fight -35kg Champion
• 2011 TRIBELATE -35kg Champion
• 2011 M-1 Junior -35kg Champion[26]
• 2011 King of Strikers -40kg Champion
• 2012 Windy Kick Jr 40kg Champion[27]
• 2013 GLADIATOR Kick Jr 45kg[28]
• 2013 Trang Province 45kg Champion[29]

• Punpanmuang
  • 2014 Punpanmuang Mini Flyweight Champion[30]

• True4U Muaymanwansuk
  • 2017 True4U Flyweight Champion[31]

• KNOCK OUT
  • 2018 KING OF KNOCK OUT Flyweight Champion[32]

• International Boxing Federation Muaythai
  • 2019 IBF Muay Thai World Flyweight Champion[33]

• World Professional Muaythai Federation
  • 2019 WPMF World Flyweight Champion[34]
  • 2020 WPMF World Super Flyweight Champion[35]

• The Battle of Muay Thai
  • 2020 Battle of Muay Thai Super Flyweight Champion (1 defense)

• World Boxing Council MuayThai
  • 2022 WBC MuayThai World Super Flyweight Champion[36]

• K-1
  • 2022 K-1 Bantamweight World Grand Prix Runner-up