In 1983, at the age of 15, Simon took part in the Miss California Teen USA where she was placed 1st runner-up. Upon her return to Thailand, she participated in the 1988 Miss Thailand pageant held in Bangkok where she won the right to represent Thailand at the Miss Universe pageant.

At age of 20, Simon was crowned as Miss Universe 1988 by outgoing titleholder Cecilia Bolocco on May 24, 1988 in Taipei, Taiwan, Republic of China. She became the second Thai woman to win the title after Apasra Hongsakula who won Miss Universe 1965. She entered the semi-finals in fourth place, right behind the United States, the Dominican Republic, and Korea. She received an interview score of 9.730, a swimsuit score of 9.684 and an evening-gown score of 9.752. Simon became the first woman ever to win both the Miss Universe and Best National Costume award in one pageant. At the time of Miss Universe 1988, Simon weighed 114 pounds, standing at 5’8″. After a year of reigning as Miss Universe 1988, Simon gave a farewell walk and speech, then crowned her successor, Miss Universe 1989, Angela Visser of Netherlands. The ceremony was held in Cancun, Mexico.

In 1989, she was named United Nations Goodwill Ambassador of Thailand by Air Chief Marshal Siddhi Savetsila, Minister of Foreign Affairs of Thailand. As Goodwill Ambassador, she addressed the UN General Assembly concerning the Convention on the Rights of the Child. She graduated with a bachelor’s degree psychology from Pepperdine University.

In 2002, she married Herbert Simon, an American businessman who is the owner of the Indiana Pacers basketball team and Simon Property Group.

Porntip Nakhirunkanok was born in Bangkok, Thailand. Her nickname is “Bui” (Thai: ปุ๋ย, RTGS: Pui, pronounced [pǔj]), which is her preferred name. It means “to sleep like a baby” in Thai. In the early 70’s, she was brought to the United States by her family. She had a younger sister who had died in 2005. In August 1988, Nakhirunkanok was presented the Thai Royal Medal of Honour, Most Exalted Order of the White Elephant, by King Bhumibol Adulyadej for her service in helping needy children. She received a second Royal Decoration in 2001, Companion of the Most Noble Order of the Crown of Thailand.