Nichkhun was born in Rancho Cucamonga, California to a Thai Chinese family.  Both of his parents are of Chinese descent.  Nichkhun has one older brother Nichan, and two younger sisters, Nichthima (Yanin) and Nachjaree (Cherleen). At the age of two, he moved to Thailand with his family and studied at Dhepkanjana School and Tangpiroondham School. At the age of twelve, he studied at Wanganui Collegiate School in New Zealand for a year and a half and moved back to the United States to finish his schooling at Los Osos High School in Rancho Cucamonga, California.
After high school, he was a coach at Rosemead High School for their badminton team. There, he was scouted by Park Jin-young, a K-pop singer and the producer of JYP Entertainment, at the Los Angeles Korean Music 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 in 2006 as a trainee, being put into a class of 24 other students.
Park Jin-young informed him that he was required to learn Mandarin Chinese and Korean to also work out regularly and learn how to dance and to sing. First appeared through MNET’s Hot Blood, a program that showed the intense physical training that 13 male trainees had to go through for the opportunity to debut in either 4-member ballad group 2AM or 6-member dance group(which had 7 members until one of them left the group) 2PM under JYP Entertainment. [