The 18-year-old winger recently impressed at the Terborg Toernooi in the Netherlands, where he was crowned as the Player of the Tournament and also won the Golden Boot with five goals from five matches.
Thethani has since started pre-season training at Ikamva under head coach Stanley Menzo, whose technical team has been boosted by the arrival of former Santos mentor Boebie Solomons.
“I was born into a family that had the love of football and when I started playing at the age of eight I had all the support from my family and that motivated me to achieve more in football,” Khayelitsha-born Thethani told Ajax's website.
“Now that I am in the first team that doesn’t mean I have made it, there is no time for me to relax.
“Basically what it means to me is that I must work hard because at the end of the day it will pay off.”
Thethani is comforted in knowing that the likes of rising star Grant Margeman will help him make the transition to senior football.
“Having guys like Grant Margeman, Luthando Mateza and Sergio Kammies in the first team will also help in the transition because I have played with them before,” he added.