Australian Adam Groom is three shots off the pace in equal third after the first round of the Brunei Open on Thursday.

Groom shot a six-under 65, which included two eagles, and sits behind leader Thai Thammanoon Srirot who shot a course-record 62 and Bangladeshi Siddikur, who shot 64, including one of the day's two hole-in-ones.

The other hole-in-one hitter was Chinese Tapei's Sung Mao-chang, who found the target in one at the 14th, but ended with a three-over 74.

Korea's Lee Sung shares third place with Groom, but the day belonged to Thammanoon, whose flawless first round included nine birdies and he was suitably rapt to have the outright lead going into Friday.

"I’m very impressed with my game. Everything was perfect from my drive, irons and putting. It was all working 100 percent. I’m prepared for the challenge this week and if I can keep up my form for the next three days, I might be able to win it," Thammanoon said, whose last Asian Tour victory was way back in 2004.

31-year-old Groom got off to a brilliant start with an eagle on the fifth hole, finding the cup from 120 yards.

"It was great to have two eagles in my round. It was a good way to start. It has been a while since I had two eagles in one day," Groom said.

"I have been trying to keep myself busy with small tournaments in Australia since losing my card. I also took a six-week break from golf to go for a holiday with my parents which was quite refreshing," added the Australian.