The 2011 Masters Tournament winner was bogey-free at the US$1 million Asian Tour event as he signalled his intent to go one better after finishing runner-up at Amata Spring Country Club last year.
Highly rated Thai youngster Thitiphun Chuayprakong, who finished third at the Venetian Macau Open in October, eclipsed many of the world's top players with a superb 66 to outscore reigning Masters Tournament winner Bubba Watson (68), Europe's Ryder Cup star Sergio Garcia (69) and title holder Lee Westwood (70).
The 20-year-old Thai put on a battling display to trail the slender Schwartzel by one in the penultimate event of the 2012 Asian Tour season.
Asian Tour Qualifying School graduate Javi Colomo of Spain continued his recent good run by making a crucial eight-foot par save on the last for a share of third place with Sweden's Daniel Chopra on matching 67s.
Schwartzel, who has finished fifth, third and second in his last three events, continued to show form that earned him his first Major win last year after recovering from a chest injury which affected much of his game this season.
"I'm just playing injury free and that's allowing me to swing the club better. When you are playing with injury, you always try to protect that injury and the consequence is a bad swing. In the last month and a half I've been able to get my swing back to where I want it to be. My consistency is coming back and that's the key for me," said Schwartzel, who sank six birdies on the card.
The world number 27 is aiming to nail his first victory since his Masters triumph but knows he must continue to overcome the steamy and humid conditions at Amata Spring. "It definitely affects you. It is as hot as I've gotten on a golf course for a long time. I suppose all you can do is take a lot of liquid. There's no escaping the heat. You just got to grind it out.
"It is nice to put yourself in position. You won't win a golf tournament in the first round but you sure can lose it. I've got no expectations. I feel that if I continue to play like how I did then I can find the result which I'm looking for. It is still early days to predict anything right now," he added.
Having secured his Asian Tour card for 2013, Thitiphun, currently 44th on the Order of Merit, played without fear as he charged up the leaderboard with six birdies to mix with the top stars.
"I've got no pressure at all. I started working with a mental coach and it's been helpful. He has told me to stay in the present and not get ahead of myself. I certainly didn't expect to shoot a six under round as my goal was four or five under," said Thitiphun.
The Thai, who is nicknamed 'Totem' by his friends which means slow because he does things in his own pace, hopes to put in good use of his experience of being in contention at the 2011 Indonesian Masters and Venetian Macau Open in October where he finished tied third on both events.
"I know I must be more patient if I'm in that situation again and not rush my game. I need to control myself better the next time," he said.
Spanish newcomer Colomo, with wife Cristina on the bag as his caddie, continued his fine run on the Asian Tour as he shot five birdies. "I want to keep the concentration and the intensity in all the shots. Today I didn't make too many mistakes. I putted really good. Cristina helps me to read the greens. She reads the greens really nice," smiled Colomo.
Big-hitting Watson drew the crowds out in his morning round but endured a mixed day with six birdies, one eagle and four bogeys to end the day three back from Schwartzel in his debut appearance at the Thailand Golf Championship, now the premier championship in Thailand due to the quality of the field.
"It didn't feel that good. It was a solid round but I made a few mistakes. Hit a cart path and bounced into the woods and had to take an unplayable and had a three putt on 17. Just little things like that. I finished with a birdie on the last so all in all, I guess it's not too bad," said Watson.
Chopra, who grew up India, wielded a red-hot putter as he sank 23 putts in a blemish free round with five birdies.
"I putted beautifully, even the putts that didn't go in. I had a whole bunch that hit the edge of the hole. So it was beautiful. I love coming back and putting on these greens in Asia. I feel comfortable on them and they are easy for me to read," said Chopra.