Kritsada Namsuwan gained his first international experience in 2011 when he retired at the Youth World Championships near Lille with 10.92 seconds in the 100 meter run in the first round and also with the Thai sprint relay (1000 meters) in 1: 57.19 minutes did not reach the final. The following year he reached the semi-finals at the Junior Asian Championships in Colombo over 100 meters, in which he was eliminated with 10.88 s and won the gold medal in the 4 x 100 meter relay in 40.21 s. He also qualified for the Junior World Championships in Barcelona , where he was eliminated with the relay with 39.68 s in the preliminary round. In 2013 he took part in the Asian Championships in Pune for the first time, but failed there with 10.90 s in the first round, as well as at the 2014 Asian Indoor Athletics Championships in Hangzhou in the 60-meter run with 7.08 s. He then reached fourth place in the season in 39.08 s at the Asian Games in Incheon, South Korea .
In 2015 he was fifth at the Asian Championships in Wuhan with the relay in 39.98 s and in 2017 he won the silver medal behind the team from China in 39.38 s at the Asian Championships in Bhubaneswar . In addition, he reached the semi-finals over 100 meters and was eliminated there with 11.78 s. Then he won at the Southeast Asian Games in Kuala Lumpur in 10.43 s the bronze medal in the individual competition behind the Malaysian Khairul Hafiz Jantan and Eric Cray from the Philippines. In addition, he won the season with a new player record of 38.90 s and then took part with the season in the Summer Universiade in Taipei , where he came in fifth in 39.22 s. The following year he took part with the relay again in the Asian Games in Jakarta and reached there after 39.29 s in sixth place.
Personal best
100 meters: 10.39 s (−1.1 m / s), January 7, 2014 in Suphan Buri
60 meters (hall): 7.08 s, February 15, 2014 in Hangzhou