April, who won the race in 2011 and 2013, secured victory in 2:11:27 on Sunday after breaking clear of a small lead group in the closing stages.
Lusapho is now amongst a long list of South African men who have already achieved the qualifying standard of 2:19:00 for the 42km race at the Rio Olympics, but await the decision of ASA on who makes the final team.
Amongst other leading contenders are Stephen Mokoka (2:07:40), who has the option to race on the track after qualifying in the 5 000m and 10 000m events, Sibusiso Nzima (2:11:43), Lungile Gongqa (2:11:59) and Michael Mazibuko (2:12:29).
"Congratulations to Lusapho April and encourage him to remain focus as he builds up his athletics season. The performance of our runners are proving that South Africans are becoming a force to reckon with in 2016 as we build up to the Rio Games," said ASA president Aleck Skhosana.
"We wish him and all other Olympic contenders well for the remainder of the season, as they represent our nation with pride on the global road running circuit.
