Nachimuthu compiled a three-day total of 11-under-par 205 for a one-shot advantage over Thailand's Jakraphan Premsirigorn, who returned with a 70, at the USD 65,000 Asian Development Tour (ADT) event.
Local Nicholas Fung signed for a 71 to take third place on 207 while Filipino Rufino Bayron surged into contention with a bogey-free 68 for fourth at the Sarawak Golf Club.
Thailand's Pavit Tangkamolprasert and S. Murthy of Malaysia took a share of fifth place after signing for rounds of 67 and 68, respectively.
Nachimuthu, who returned this morning to complete his second round, mixed his card with four birdies against two bogeys. He is hopeful that he can continue to capitalise on his lead and turn it into victory Sunday.
"I missed some putts today but overall I'm happy with how I played. I'm reading the greens better now. I just hope to stay focused on my game and hopefully win tomorrow," said the 42-year-old as he put himself in prime position for a maiden win on the ADT.
With only three more events to play on the ADT before the season ends, players will have everything to play for as they vie to finish in top-3 on the Order of Merit which will earn them playing rights on the 2014 Asian Tour.
205 - R. Nachimuthu (MAS) 65-70-70
206 - Jakraphan PREMSIRIGORN (THA) 69-67-70
207 - Nicholas FUNG (MAS) 66-70-71
208 - Rufino BAYRON (PHI) 73-67-68
209 - Pavit TANGKAMOLPRASERT (THA) 73-69-67, S. Murthy (MAS) 72-69-68
210 - Faridil ATRAS (MAS) 71-71-68, Darren TAN (AUS) 71-70-69, Masaru TAKAHASHI (JPN) 70-70-70, Charles HONG (PHI) 73-67-70, Adam BLYTH (AUS) 72-67-71, Hans JAMIL (MAS) 67-70-73.
--IANS (Posted on 05-10-2013)