Mlwane spent the last six months with Malanti Chiefs where he steered them to a top-eight finish in the same league.
The ex-Moroka Swallows man, who previously coached Moretele Gunners in the North West's ABC Motsepe League, appears determined to improve his CV across the border.
"There has been negotiations going on but nothing finalised yet," says Manzini Sundowns boss Mark Carmichael.
"We spoke and he sounds like a guy who wants to work hard and improve his CV."
Former Black Leopards mentor Mlungisi Ngubane is coaching Mbabane Highlanders in the neighbouring country.