Despite having large amounts of land, Vorapin, his parents, and his 14 siblings were impoverished farmers, as the mountainous ground was poor soil for agriculture.
Because of his poverty, he became a boxer at age fourteen in Muaythai using the names "Tonaonoy Toichainee" (ทนเอาหน่อย ต่อยใช้หนี้) and "Lion Luknamjai" (ไลอ้อน ลูกน้ำใจ) sponsored by Yindee Juntacup, a local celebrity.
When Fahlan Lukmingkwan lost the IBF Mini flyweight championship to Filipino Manny Melchor in mid-1992, Ratanapol was encouraged by Sr. Col. Banju Ongsangkune and Suchart "Pe Poster" Kerdmek to return to Thailand.
On December 10, 1992, at Nimibutr Stadium, he scored a 12-round split decision victory over Manny Melchor to win the Mini flyweight title.
On May 18 the same year, however, he returned as the world champion and he retained it six times until December 27, 1997, when he received a 5th-round TKO loss to South African Zolani Petelo at Songkhla province, southern Thailand.