KUALA LUMPUR, Sept 5, 2012 (AFP) - The 45-year-old, whose record 13 Asian Tour titles include two victories in Malaysia, carded one eagle, four birdies and a lone bogey at the Kota Permai Golf and Country Club.
Australia's Marcus Both was also six-under through 12 holes when play was suspended at 7.05pm. Michael Tran of Vietnam was five-under with three more holes to play.
American Jonathan Moore, the reigning Asian Development Tour (ADT) Order of Merit champion, recovered from two early bogeys to shoot a 67 for second place while Javi Colomo of Spain was a further stroke back in the RM1.2 million ($400,000) Asian Tour event.
A total of 59 players will return on Thursday morning to resume their opening rounds after an afternoon thunderstorm disrupted Wednesday's play for two hours.
Arnond Vongvanij and Prom Meesawat of Thailand were tied in fourth place on 69 along with Malaysia's Nicholas Fung, Bangladeshi newcomer Zamal Hossain and Jhonnel Ababa of the Philippines.
"Nowadays I'm very relaxed. I come to play, see good friends. I'm 46 (in December), no longer a young boy but I still enjoy going out to compete," Thaworn said, according to a press release from the Asian Tour.
Beginning on the 10th tee, the unorthodox swinging Thaworn produced a fast start with an eagle on the par five 12th hole, when his three wood approach shot hit the pin.
"I've played many times on this golf course and I've never hit that green in two on 12. So I got lucky there. I made a lot of pars and then made birdie on 18 from a downhill putt. It is a difficult course. Downhill putts are really fast," he said.
Top 10 scores after round one of the Worldwide Holdings Selangor Masters:
66 - Thaworn Wiratchant (THA)
67 - Jonathan Moore (USA), Panuphol Pittayarat (THA)
68 - Javi Colomo (ESP), Jhonnel Ababa (PHI), Lu Tze-shyan (TPE)
69 - Arnond Vongvanij (THA), Nicholas Fung (MAS), Prom Meesawat (THA), Zamal Hossain (BAN)