Rangsan Viwatchaichok (Thai: รังสรรค์ วิวัฒน์ชัยโชค; RTGS: Rangsan Wiwatchaichok), born 22 January 1979) is a Thai professional football manager and former player who is currently the head coach of Thai League 1 club Chonburi.

Rangsan currently holds the record for the most all-time appearances in Thai League 1, with 439 appearances. He is known for his set pieces freekick back in his playing career.

Rangsan has played 29 games for the senior Thailand national team since 2004, and he has scored one goal in the process.

On 11 July 2013, BEC Tero Sasana sacked René Desaeyere and promoted Choketawee Promrut to be the club interim manager. Rangsan, who was the club captain, was also promoted to be the assistant coach.

On 9 August 2015, Rangsan was promoted to be the interim manager of BEC Tero Sasana after the removal of Kenny Shiels.

He had coached the club for three games before the appointment of Manuel Cajuda on 27 August.

On 1 December 2015, he was promoted to be the interim manager again after the resignation of Manuel Cajuda. Rangsan managed the club in the last three games of 2015 season with the record of 2 wins and 1 loss. The club set to relegate to Division 1 according to the final standing but still remained in top league after the withdraw of Saraburi from the competition.

On 17 April 2017, Rangsan was appointed as assistant manager of Suphanburi under manager Adebayo Gbadebo.