It was one of two massive wins for pre-tournament favourites on the day as Zambia were equally impressive in a 5-1 victory over Zimbabwe in Group B.
South Africa were always in control of their fixture and scored their goals through Itumeleng Shopane, Luther Singh (penalty), Wisemen Meyiwa, Nkosingiphile Ngcobo, Sifundo Sibiya, Menzi Ndwandwe, Sibongakonke Mbatha and Achmat Ceres.
They led 3-0 at the break and piled on the pressure in the second period, leaving Lesotho at times chasing shadows.
In the second match in Group A, Swaziland got their tournament off to a winning start with a 2-0 success over Botswana thanks to goals in either half from Bhekani Mthembu and Ali Matse.
Swaziland were dominant in the game and might have won by a greater margin, but could be pleased with their first win over Botswana in this tournament for 24 years.
Zambia took a giant step towards the semifinals with a crushing 5-1 victory over their old rivals.
The Young Chipolopolo, 10-time winners of the COSAFA Under-20 Championships, were imperious as goals from Patson Daka, Edward Chilufya, Chrispen Sakulanda, Fashion Sakala and Moses Nyondo sealed their win.
Bukhosi Sibanda scored a consolation or Zimbabwe from the penalty-spot.
Thursday’s matches at the Mogwase Stadium see the opening two games in Group C, including a tasty meeting between Angola and North African guest nation Sudan (kick-off 17h00).
Sudan have qualified for the African Youth Championships in Zambia in February, knocking out powerhouse Nigeria along the way.
Angola have brought much of their squad that competed at the COSAFA Castle Cup senior tournament in Namibia in June.
There is also a clash between the island nations of Seychelles and Mauritius (14h00), which would give these two sides a rare opportunity for a victory.
Earlier, central African guest DR Congo take on Mozambique in a crucial battle in Group D (11h00). Both will be eager to get their campaigns off to a positive start with Comoros Islands the third team in that pool.
Swaziland 2 (Mthembu 34’, Matse 76’) Botswana 0
South Africa 8 (Shopane 12’, Singh 17’pen, Meyiwa 35’, Ngcobo 50’, Sibiya (South Africa), Ndwandwe 76’, Mbatha 83’, Ceres 89’) Lesotho 0
Zimbabwe 1 (Sibanda 87’pen) Zambia 5 (Daka 41’, Chilufya 44’, Sakulanda 60’, F Sakala 80’, Nyondo 90’)
14h00 (12h00 GMT): Seychelles vs Mauritius – Mogwase Stadium
17h00 (15h00 GMT): Angola vs Sudan – Mogwase Stadium
11h00 (09h00 GMT): DR Congo vs Mozambique – Mogwase Stadium