[1] Sanmahung made national headlines in 2018 when he became the youngest player to score for Chonburi, doing so for the club's 'B' team in the Thai League 4.
[2] For the 2020 season, he was loaned to Thai League 3 side Banbueng, alongside teammate Warakorn Thongbai.
In 2021, he stepped up to the Thai League 2, signing on loan for Khon Kaen United, again making the move with Thongbai.
[6][7] While representing Thailand U16, Jakkapong scored against Northern Mariana Islands U16 in the 2018 AFC U-16 Championship qualification.
[9] Jakkapong is the brother of fellow professional footballer Nitipong Sanmahung.