Nichkhun was born in Rancho Cucamonga, California to Thai parents. His father is of Thai origin while his mother is a fourth generation Thai Chinese. Nichkhun has one older brother and two younger sisters. At the age of two, he moved to Thailand with his family, but moved back to the United States to finish schooling in Los Osos High School in Rancho Cucamonga, California. There, he was scouted by Park Jin-young, a K-pop singer and producer of JYP Entertainment, at the Los Angeles Korean Festival.
After passing the audition hosted by JYP Entertainment, he signed a ten-year contract with the company but later resigned for an eight-year contract, not including training, and was brought to South Korea as a trainee, being put into a class of 24 other students. Park Jin-young informed him that he was required to learn Korean and Mandarin Chinese to also work out regularly and learn how to dance. There is a Korean show called "Hotblood," showed in 2008, which shows Nichkhun and many others as trainees of JYP Entertainment. From there, you can see how hard being a trainee of JYP Entertainment was.
Nichkhun participated in JYP's talent competition, Superstar Survival, where he took the role of the host.