GREATER NOIDA, India, March 15, 2013 (AFP) - Chapchai and Liang carded identical six-under-par scores in each of the first two rounds of the $2.3 million event at the Greg Norman-designed par-72 Jaypee Greens course outside New Delhi to leave them joint top on 12-under.
"I played very well indeed," said Chapchai, a three-time winner on the Asian Tour who is looking for his first European Tour title after six years.
"I have adjusted well to the long course. I also managed to hole several long putts as well, but I am lucky to be sharing the lead at this stage."
Liang, the first player from mainland China to win the Asian Tour Order of Merit in 2007, joined Chapchai with eight birdies against two bogeys in the second round.
"I feel recharged after taking a break to spend time with my family," he said. "I have played some of my best golf this week and I managed to hole several long putts.
"There are still two more rounds to go and, hopefully, I can be atop the leaderboard like today."
Thailand's Chawalit Plaphol, David Drysdale of Scotland, Tommy Fleetwood of England and Finland's Joonas Granberg all lay two strokes behind the leaders at 10-under.
Fleetwood carded a seven-under 65 -- later matched by Brazilian Adilson Da Silva (BRA) -- to keep himself in the hunt.
Chinnarat Phadungsil of Thailand, whose astonishing 28 on the back nine on Thursday gave him the lead with 11-under par 61, failed to conjure the same magic on the second day.
An inconsistent run of bogeys but five birdies saw him finish the day with two-over 74 for a combined tally of nine-under 135.
"It's not over for me yet. If I play like yesterday, all will be forgotten," he said.
Scotland's Montgomerie, one of the tournament's star attractions, will not be involved in the weekend's play after two rounds of 76.
India's richest golf event, now into its fourth year, is co-sanctioned by the European and Asian Tours.
Leading scores after the second round in the $2.3 million Avantha Masters golf at the Jaypee Greens in Greater Noida on Friday:
132 - Chapchai Nirat (THA) 66-66, Liang Wenchong (CHN) 66-66
134 - Chawalit Plaphol (THA) 66-68, David Drysdale (SCO) 67-67, Tommy Fleetwood (ENG) 69-65, Joonas Granberg (FIN) 67-67
135 - Chinnarat Phadungsil (THA) 61-74, Rahil Gangjee (IND) 69-66, Scott Hend (AUS) 67-68, Abhijit Chadha (IND) 66-69, Jaakko Makitalo (FIN) 67-68, Julien Quesne (FRA) 69-66, Adilson Da Silva (BRA) 70-65.
136 - Thomas Aiken (RSA) 67-69, Rikard Karlberg (SWE) 67-69, Maximilian Kieffer (GER) 68-68, Baek Seuk-Hyun (KOR) 68-68, Pablo Larrazabal (ESP) 68-68, Kiradech Aphibarnrat (THA) 68-68
137 - Brett Rumford (AUS) 68-69, Mark Foster (ENG) 70-67, Jeev Milkha Singh (IND) 69-68, Victor Dubuisson (FRA) 69-68, Peter Whiteford (SCO) 68-69, Gaganjeet Bhullar (IND) 68-69, Anirban Lahiri (IND) 68-69
138 - Paul Waring (ENG) 70-68.
139 - Mardan Mamat (SIN) 68-71, Magnus Carlsson (SWE) 66-73, Lee Slattery (ENG) 72-67, Scott Barr (AUS) 67-72, Andy Sullivan (ENG) 71-68, Ashok Kumar (IND) 68-71, Soren Kjeldsen (DEN) 72-67, Martin Wiegele (AUT) 72-67, Matthew Baldwin (ENG) 69-70, Emiliano Grillo (ARG) 68-71, Maarten Lafeber (NED) 73-66.