Fighting in
Lumpini Stadium, Clancy took on Matt Sheady. He won the fight by a second round TKO, after a series of knees and elbows. During Cage Kings' inaugural event, Clancy fought against his fellow Irish Nak Muay Paul Budden. Clancy won the fight by a unanimous decision. Clancy stepped in as a late notice replacement to face the multi divisional
Lumpini Stadium champion
Saenchai during THAI FIGHT Samui 2016. Clancy lost in the third round, by TKO. Clancy fought for the Caged Muaythai Super Lightweight tile against Matthew Bune during CMT 10. Cage Muaythai differed from the usual muaythai fights in that the competitors fought in the 4 oz gloves, typically used in
mixed martial arts, instead of the larger boxing gloves. Clancy won the fight by a fourth round TKO. In 2018 Clancy participated in the
K-1 Super Lightweight Tournament, being scheduled to face Jun Nakazawa in the
tournament quarter finals. Clancy lost the quarter-final bout, losing by TKO in the very first round of the fight. Sean Clancy fought against Roy Willis for the International Super Lightweight WBC Muaythai title during Lion Fight 52. Clancy won the fight by split decision, with two judges scoring in his favor (48-47, 49-48) and one judge scoring the fight for Willis (50-45). Following his capture of the WBC Muaythai International title, Clancy was given an opportunity to fight for the World Super Lightweight title as well. He was scheduled to face Alessandro Sara at the Neptune Stadium in
Cork. Clancy won the fight through a unanimous decision. He afterwards fought during Lion Fight 60 against Ramesh Habib for the Lion Fight World Super Lightweight title. He was unable to mount a comeback after being dropped in the first round, and lost a unanimous decision. Clancy's first fight in
ONE Championship was against
Pongsiri P.K.Saenchaimuaythaigym, during
ONE Championship: A New Breed 2. Clancy lost a unanimous decision. Clancy faced
Tawanchai P.K. Saenchaimuaythaigym at
ONE Championship: Dangal on 15 May 2021. He lost the bout via head kick knockout at the beginning of the third round. ==Championships and accomplishments==