Lewis has selected a 34-man training squad which will be reduced next month after a period of training sessions. The decision to travel to South Africa and play these games was taken, in part as a result of the review undertaken following last year's Junior World Championship in Italy when Wales lost 92-0 to New Zealand and lost to Fiji.
Lewis said, "This festival of rugby will be a fantastic experience for this group of players. Not only will they gain from the training and preparation period leading up to selection in the first place, but those selected will get to play the likes of South Africa, France and England away from home in the southern hemisphere, benefitting from the whole experience both on and off the field.
"It will doubtless aid their development towards their potential inclusion in the Junior World Championship squad for next season and / or the following season as it will give the players a first, real taste of global rugby.
"Along with South Africa, France and England are two of the strongest teams in the world at age grade level, but the fact that we are playing these teams in South Africa itself will make it even more valuable, and potentially something we would like to organise on an annual basis."
The squad leaves for South Africa on Monday 6 August and returns on Sunday 19 August with games in Stellenbosch and George.
Wales Under 18 Development tour fixtures
Wales Under 18 Development XV v England - Fri Aug 10 Boland Rugby Stadium, Wellington, Stellenbosch
Wales Under 18 Development XV South Africa - Tues Aug 14 Outeniqua park Stadium, George
Wales Under 18 Development XV France - Sat Aug 18 Paul Roos School, Stellenbosch
Wales Under 18 Development XV training squad:
Forwards: Callum Jay Lewis (Blues), Nicky Smith (Ospreys), Nicky Thomas (Ospreys), Jack Dunning (Blues), Rhodri Evans (RGC 1404), Alex Jeffries (Dragons), Elliot Dee (Dragons), Thomas Ball (Scarlets), Ethan Lewis (Blues), Joshua Helps (Scarlets), Lance Randell (Dragons), Sean O'Rourke (Ospreys), James Sheeky (Blues), Sion Bennett (Scarlets), Scott Matthews (Dragons), Joseph Tomalin-Reeves (Ospreys), James Benjamin (Dragons), Benjamin Roach (Blues), Scott Andrews (Dragons).
Backs: Connor Lloyd (Scarlets), Gareth Rees (Scarlets), Will Batcup (Ospreys), Jack Maynard (Scarlets), Ethan Davies (Dragons), Ryan Evans (Ospreys), Steffan Hughes (Scarlets), Ben Roberts (Ospreys), Craig Woodall (Scarlets), Dylan Morgan (Scarlets), Dafydd Wyn Howells (Ospreys), Lewis Hudd (Dragons), Jake Randell (Scarlets), Hallam Amos (Dragons), Dion Jones (Scarlets)