Early career Sam-a began fighting at age 9 after following the career of his uncle and watching Muay Thai on TV. Within a few years he had already had a couple hundred fights and was fighting nearly every week. At 15 he moved to
Bangkok and began training at the Petchyindee Muay Thai academy.
Stadium Success By the turn of the century Sam-A was fighting at both
Lumpinee boxing stadium and
Rajadamnern boxing stadium. He won his first stadium title in 2004 when he beat
Petch T. Bangsean for the super flyweight championship of Lumpinee. Soon after he won the Thailand championship at the same weight.
2008 By 2008 he was one of the biggest stars in Muay Thai and was frequently headlining major shows. At the beginning of the year he beat
Petchboonchu FA Group for the vacant Thailand bantamweight title, and shortly after beat him again by a stoppage from an accumulation of kicks. Following a loss to Captainkane Narupai, Sam-A would stop top-tier fighters, Jenrop Sakhomsin,
Penek Sitnumnoi, and Rungruanglek Lukprabart all in a row. He closed the year out by capturing the Lumpinee championship with a win over Detnarong Wor. Sangprapai.
2009 - 2010 Sam-a continued his great run of fighting in 2009 by starring in a classic rivalry with fan favorite,
Pornsanae Sitmonchai. Within a 12-month period the two would go on to fight 5 times, with Sam-A winning 4 of those. His single loss would come in 2010 from a controversial knockdown called late in the fight. In this time, he emerged as a "Yodmuay" (super fighter) and became one of the few fighters in Thailand who were making 100,000 baht per fight. In 2010 he split wins over another rival, Rungruanglek Lukprabart. Towards the end of 2010, he would move up to 126 pounds and challenge top fighter
Nong-O Sit Or at Lumpinee Stadium. Soon after, he would stay up in weight and again lose to a bigger fighter,
Singtongnoi Por.Telakun. The size difference proved to be too much for Sam-A.
2011 - 2012 In 2011, he came back down to his natural weight and surpassed his 2008 year by going 8-0-1 and winning the Lumpinee Fighter of the Year award. His fight with reigning Fighter of the Year
Kongsak Sitboonmee was amongst the biggest and most anticipated of the year. The fight was very close at the end and was ruled a draw. Soon after Sam-A's promoter told him he would buy him a new
Toyota pickup truck if he won five straight fights. Sure enough he did, and Sam-A was awarded with a new Toyota pickup valued at over $50,000 after a dominant decision win over Tingtong Chor. Koyahu-Isuzu. In 2011, he changed his name from Sam-A Thor. Ratonakiat to Sam-A Gaiyanghadaogym. Despite having "gym" in the name, it is nothing more than a sponsor, with "Gaiyanghadao" literally meaning "5-star grilled chicken". For his first fight of 2012, he defeated Rungruanglek Lukprapbart by unanimous decision, and in doing so may have finished a long rivalry between the two with a 4–3 record head-to-head. The only other fighter he has fought 7 times was
Yodsaenklai Fairtex. On May 4, Sam-A fought
Penake Sitnumnoi at Lumpinee Stadium with the winner expected to receive the prestigious Fighter of the Year award. Penake dropped Sam-A with an elbow in the fourth round and won by unanimous decision. During the fight, Sam-A suffered a thigh injury which caused him to stop training Muay Thai and turn to
boxing instead.
Professional boxing On July 12, 2012, Sam-A had his first career professional boxing match. He fought Christian Abila and won by 4th-round TKO. He made his Muay Thai comeback on August 6 and defeated Tong by unanimous decision at Lumpinee Stadium. He was scheduled to rematch
Penake Sitnumnoi on October 4, 2012, at Lumpinee but the fight was postponed when Penake suffered a shoulder injury. He beat
Petpanomrung Wor Sungprapai by decision at Lumpinee Stadium on November 2, 2012.
2013 - 2014 Sam-A rematched Pokaew Fonjaenchonburi on February 7, 2013, and the pair fought to a draw. He beat Yokwitaya Petsimean on points at Lumpinee Stadium on May 10, 2013. He TKO'd
Phet Utong Or. Kwanmuang in round two at Lumpinee Stadium on June 7, 2013. Sam-a beat
Superlek Wor Sangrapai on points to win the vacant Thailand super bantamweight title at Lumpinee Stadium on July 12, 2013. On October 21, 2014, Sam-A defeated Andrew Doyle by fourth-round KO to win the WBC World 60 kg Title
2016 On July 29, 2016, Sam-A fought Japanese kickboxer, Yuya Kono in Japan. He stopped Kono in the third round with an elbow knockout. Sam-A retired from fighting following the fight and moved to Singapore where he joined
Evolve MMA as a Muay Thai instructor. He followed that up with a KO victory over
Sergio Wielzen on May 18, 2018, to claim ONE's inaugural
ONE Super Series Flyweight Muay Thai World Championship at
ONE Championship: Unstoppable Dreams.
2019 In his first title defense on May 4, 2019, he lost the title in upset fashion to England's
Jonathan Haggerty by unanimous decision at
ONE Championship: For Honor. Following his title loss, Sam-A Gaiyanghadao moved down to
strawweight and eventually made his return to ONE Championship on October 13, 2019, at Tokyo. He faced
Darren Rolland in Part 1 of
ONE Championship: Century, where he knocked out the Frenchman in the second round. Sam-A Gaiyanghadao then faced
Wang Junguang for the inaugural
ONE Strawweight Kickboxing World Championship at
ONE Championship: Mark Of Greatness on December 6, 2019. Sam-A defeated Wang Junguang by unanimous decision to become the first ONE Kickboxing Strawweight World Champion, as well as the second two-sport World Champion in ONE Championship.
2020 Next, Sam-A was looking to win a second title as he faced Rocky Ogden for the inaugural
ONE Strawweight Muay Thai World Championship at
ONE Championship: King of the Jungle on February 28, 2020. After dominating the entire fight, Sam-A would go on to win by unanimous decision and become the first ONE Muay Thai Strawweight World Champion, becoming ONE Championship's second two-sport world champion in the process. Sam-A was then scheduled to make his first defense of the ONE Strawweight Muay Thai World Championship against Josh Tonna, who was coming off a two straight wins. The two faced at
ONE Championship: Reign of Dynasties on October 9, 2020. Coming into the fight as a huge favorite, Sam-A defeated Tonna via second-round TKO after delivering three knockdowns to retain the title.
2021 Sam-A made his second defense of the
ONE Muay Thai Strawweight Championship against fellow countryman and ONE promotional newcomer
Prajanchai P.K.Saenchaimuaythaigym at
ONE Championship: Battleground on July 30, 2021. After five hard-fought rounds, he ultimately lost the title by majority decision.
2022 In February 2022, it was reported that Sam-A had retired from international competition after returning to Thailand from Singapore, where he had coached at Evolve MMA. On February 10, 2023,
Nuttadaj Vachirarattanawong promoter of Petchyindee Academy announced Sam-A has not retired due to arm injury and want to return to Thailand for treatment, but the ONE team fired them back and released the news that Sam-A had retired. Chitinat Asadamongkol, president of ONE Championship Thailand, stating that organization has never released news that Sam-A will retired and Sam-A himself is still in the contract, but who went back to fight with Petchyindee battle earlier, because Nuttadaj contacted him to negotiate and there is a discussion which organization allows, with matters of this nature having to be discussed on a case-by-case basis.
2023 After won Tongnoi Lukbanyai and
Samingdam Chor.Ajalaboon at Petchyindee in
Rajadamnern Stadium, Sam-A faced
Ryan Sheehan on March 17, 2023, at
ONE Friday Fights 9. He won the fight via knockout in the second round. Sam-A faced
Prajanchai P.K.Saenchai in a rematch at
ONE Friday Fights 22 on June 23, 2023, for the interim
ONE Muay Thai Strawweight Championship. He was knocked out with a right elbow in the second round.
2024 Sam-A faced
Akram Hamidi on September 27, 2024, at
ONE Friday Fights 81. He won the fight via knockout in the first round and this win earned a
$10,000 Performance of the Night bonus.{{Cite web |date=2024-09-27 |title=ONE Friday Fights 81 Results: Superbon Finishes Nattawut with Elbow Sam-A faced
Zhang Peimian in a kickboxing bout on November 9, 2024, at
ONE 169.{{Cite web |date=2024-10-16 |title=ONE Championship: China's Zhang Peimian faces former kickboxing champion at ONE 169
2025 Sam-A faced
Jonathan Di Bella for the interim
ONE Strawweight Kickboxing World Championship on March 23, 2025, at
ONE 172.{{Cite web |date=2025-01-31 |title=ONE Championship adds four title fights to ONE 172 in Japan, including Tawanchai vs Noiri ==Personal life==