Scott launched his campaign in Asia's richest national Open with a 70 after a spectacular start of three consecutive birdies. England's Ryder Cup star Westwood, who called Serapong the toughest course in Asia, scrambled to a 71.

After a slow start with two early bogeys in four holes, Thongchai took his familiar place at the top of the leaderboard with six birdies, including an impressive inward 31. However, he conceded he got 'lucky' with the notorious Serapong rough.

'The rough will kill everybody. I used a lot of three-woods or two-irons to put the ball on the fairway. I am really happy with that score. I holed three or four putts from just over 20 feet which were really important. I think I was lucky today. I missed four or five fairways but luckily I had a good lie each time,' said Thongchai, who successfully defended his Malaysian Open title in February.

The former paratrooper, currently second on the order of merit, is harbouring hopes of a third merit crown in five years but knows he needs a big week here. He is planning another assault at the US PGA Tour Qualifying School later this season, meaning his appearances in the region could be limited.

'A good week here and I will have a great chance. However, Thaworn [Wiratchant] is playing well and will be tough to beat. I will have to plan my schedule. I have three more Asian Tour events to play this year, and have the US PGA Tour School [second stage] to go to. If I do well here and have a chance to be number one in Asia again then I might have to change my schedule a bit,' said Thongchai.

The story of the day belonged to the 22-year-old Chapchai. The unheralded Thai, playing in only his seventh Asian Tour event and currently ranked a lowly 106th, charged to the top with a sparkling display that included five birdies.

'I kept the ball in play, just missing one fairway. I hit only three drivers out there and used my three-wood mostly from off the tee. I've been paying a lot of attention to the Singapore Open as it's a big event and there is plenty to play for,' said Chapchai.

Starting from the 10th, he drained a 20-footer for birdie on his opening hole which set the tone for the rest of his round. 'I started nicely and got a bit of confidence from there. All my other birdies were from inside 10 feet. It's good to lead as Thongchai is my hero,' said Chapchai, who turned pro at age 16.

The 25-year-old Scott, already a winner twice this season, was quickly off the blocks to thrill the large galleries. He missed birdie chances on the fourth and fifth holes before stumbling with bogeys on the eighth and 12th and a costly double bogey on 13 when he three-putted from five feet.

'I got off to a great start and apart from the double bogey on 13, everything was perfect. I had three putts from five feet on 13, I don't know what happened really, not concentrating, just one of those things,' said Scott.

The Aussie, fresh from a two-week holiday, found the punishing rough a challenge.

'It's the deepest rough I have played anywhere. It's almost like having a penalty shot when you get in there.'