Yang, Asia's first Major champion when he won the 2009 PGA Championship, enjoyed a bogey-free outing at the Sentosa Golf Club's Tanjong course and used a superb eagle to spark his strong start.
Ryder Cup star Molinari of Italy and young Englishman Morrison enjoyed birdie binges with 10 each as they topped the leaderboard with spectacular 62s in Asia's richest national Open which is sanctioned by the Asian Tour and European Tour.
Japan's Daisuke Maruyama came in with a 64 on a stifling day at Sentosa while Korea's Lee Sung, Thailand's Atthaphon Prathumanee and India's Rahil Gangjee ensured a strong Asian presence with 65s which was matched by Jbe Kruger of South Africa, who posted the best of the day at the more challenging Serapong course.
The tournament's top guns failed to fire on all cylinders. Northern Ireland's Graeme McDowell battled to a 68 at the Serapong while world number 11 Phil Mickelson, playing at the Tanjong, needed two late birdies to salvage a level par 71. Three-time Major champion Padraig Harrington returned a 69 while Ernie Els, a two-time runner-up here, returned a 72.
After starting with a birdie on two, Yang, an Asian Tour honorary member, used a 15-foot eagle on the sixth to spark a birdie run and went on to roll in five more birdies to move up the leaderboard.
"Yeah that really kick-started everything," said Yang. "Very warm today [Thursday]. I had to use a towel quite a few times before I teed off. First few shots I made were quite bad and it was disappointing. But I think it was good that I got all those bad shots out of my system early on so I could capitalise on the later holes. My putter worked very well so overall I cannot really complain."
Yang insists his tournament will only begin for him from Friday when he returns to the Serapong course. "Tomorrow [Friday] and the final rounds are going to be played on a different course, so it is going to be like a new tournament for me. I'm not thinking of the title just yet," said Yang, who had to birdie his last three holes to make the halfway cut here last year before finishing equal 16th.
The 30-year-old Molinari, who enjoyed a bumper 2010 with two victories and a maiden Ryder Cup appearance, wielded a hot putter to set the early clubhouse target. "It was a very good round. I missed a few shots out there but the putting was finally excellent which is probably the first good round of putting that I have had in a while," said Molinari.
Morrison broke through on the European Tour with a win in Portugal last year but followed up with only two top-10s this season. "It is a tough day out on the golf course when one is hard and one is a little bit easy. You always try and chase from the start. I stayed patient and played great all the way around and holed a few putts," said Morrison, who played on the Tanjong course.
With only five players from the Serapong course featuring in the top-30 of the day one leaderboard, Kruger was certainly delighted with his six-birdie round. But he refused to raise his hopes as he bids for a first Asian Tour victory.
"You can't start thinking about stuff like that. You have to take one shot at a time. I'll have to play the best," said Kruger.
"I won't call it an advantage. It's nice to start it this way but you still have to hit every shot. I'm going to try to play the same golf tomorrow [Friday]. You have to attack to shoot low. If I can hit it well, you'll never know," added Kruger, who is currently sixth on the Asian Tour's Order of Merit.
Prathumanee hit all 18 greens as he hit six birdies to feature on the leaderboard. "Everything went to plan today [Thursday]. I hit a lot of quality shots and my putting was solid. I suppose I was a bit lucky as I was drawn to play the easier course first. You need to get a score here and I did that," said the Thai.
Mickelson, the highest ranked player in this week's Barclays Singapore Open, lamented missed opportunities as he failed to take advantage of the scoreable Tanjong course by dropping one double bogey, two bogeys against four birdies.
"The scoring average on Tanjong is going to be two or three under so level par is not considered a very good round. But you can shoot low scores on the other one as well. It is just a little bit more difficult because it's a lot longer," said the American, who is a four-time Major champion.
"I didn't feel I was playing bad, I only hit one bad shot which was one bad drive on 11 [for double]. And I didn't feel like I putted poorly, I hit my putts on line. I need to play the Serapong strategically better."