2016–2019: Asian Junior champion and thrice World Junior champions Kunlavut exhibited promising performances throughout his junior-level tournament. He won junior tournaments including the boys' singles title in the Banthongyord Junior International and Singapore Youth International, and also the Junior Grand Prix title in Jaya Raya (Indonesia) and India in 2017. In the same year, he won the bronze medal at the
Asian Junior Championships. He followed up his impressive showing in the
World Junior Championships with a gold medal win. He managed to defend his title in the Banthongyord Junior International and double the title by winning the mixed doubles with
Phittayaporn Chaiwan. He then upgraded his medal in the
Asian Junior Championships to silver, losing the finals to
Lakshya Sen. However, he managed to defend his
World Junior titles. In his final year in the junior circuit in 2019, Kunlavut managed to win double title and defend his boys' singles and mixed doubles title in the Banthongyord Junior International. He finally won a gold medal at the
Asian Junior Championships, becoming the first ever Thai to win the boys' singles title, and addition a gold in the team event. Kunlavut successfully defended his
World Junior Champions title for the third time,
Polish Open,
Finnish Open, and
Spanish International.
2020–2022: World Championship silver medalist Kunlavut began the 2020 season as semi-finalist in the
Thailand Masters. He then entered the finals of the
Spain Masters losing to
Viktor Axelsen. In his debut at the
All England Open, he was stopped in the first round to
Lin Dan in rubber games. Due to the
COVID-19 pandemic, numerous tournaments on the
2020 BWF World Tour were either cancelled or rescheduled for later in the year. He played at the Super 1000
Yonex and
Toyota Thailand Open but was eliminated in the second round in both tournaments. His best result in 2021 was being one of the finalists in the
Swiss Open and in the Indonesia badminton festival the
World Tour Finals, where he was defeated by Axelsen. In 2022, Kunlavut won his first title of the year in the
German Open. At the
2021 SEA Games, he won two gold medals in both the singles and team events. Competed as the seed 16, Kunlavut claimed the silver medal in the
World Championships, where in the finals he lost to Axelesen in straight game. He then beat the current world number 1
Viktor Axelsen to claim his first title of the year in the
India Open. He then became the fourth Thai men's singles player to win the home soil title, the
Thailand Open in early June. In the following week, he suffered an injury during the semi-finals in the
Singapore Open against
Anthony Sinisuka Ginting. In July, he finished runner-up in the
U.S. Open. Kunlavut's finest hour in his career came at the
2023 World Championships. In the final, he prevailed as he defeated Naraoka in a rubber game to win the gold medal, and achieved his highest BWF world ranking of third in the men's singles category. His victory at the World Championships, making him Thailand's third gold medal winner during the
World Championships since it was first held in 1977. He qualified to compete at the
World Tour Finals as the World Champions, but was eliminated in the group stage. He closed the year as world number 7.
2024: Olympic silver Kunlavut achieved a significant milestone by winning a silver medal at the
Paris 2024 Olympics, after advancing to the final by defeating world number one
Shi Yuqi of China. He was ultimately bested by Denmark's
Viktor Axelsen in the gold medal match. His silver medal made him the first Thai athlete to earn an olympic medal in badminton.
2025: Asian Championships title and world number 1 A good start shown by Kunlavut in the beginning of the 2025 BWF World Tour, when he reached the quarter-finals at the
Malaysia Open. Despite an early loss at the
India Open, he went on to win the
Indonesia Masters. In April, Kunlavut beat
Lu Guangzu in the
Asian Championships and become the first ever men's singles title winner from Thailand. Kunlavut solidify his form by winning his home tournament,
Thailand Open in his favoured three games match against
Anders Antonsen. In June, Kunlavut won the
Singapore Open in dominating fashion against Lu Guangzu. His excellent performance in Singapore Open shot himself up into the number one in men's singles ranking, thus becoming the first Thais ever to achieve such honour in the history. Later in the year, Kunlavut lost in the final of
Arctic Open to
Chou Tien-chen.
2026 Kunlavut started the season by winning the
Malaysia Open in straight games against Shi Yuqi who had to retired due to the right shoulder injury. He became the first Thai player to win the Malaysia Open in 68 years. In April, Kunlavut was on a mission to defend his Asian Championship but lost out to
Ayush Shetty in three games. == Achievements ==