With Spain's Larrazabal and Chinese Number One Liang topping the leaderboard at Suzhou Jinji Lake Golf Club one shot clear of former champion Damien McGrane after carding opening rounds of six under par 66, Pavin and Thongchai quickly moved onto four under par.
Pavin, playing alongside Thongchai and Europe Captain Colin Montgomerie, made the first move with a hat-trick of birdies in the middle of his front nine before beginning the links half of the Gary Player-designed course with a fourth gain of the day.
Thongchai, meanwhile, was showing no ill affects of the elbow strain which forced the Thai ace to pull out before the second round of the Masters Tournament last week and picked up four shots over the final five holes on the wetlands style front nine.
But with Pavin and Thongchai forging ahead in the cold conditions just outside Shanghai, Montgomerie endured a hit-and-miss first round which left the Scot level par through 13 despite four birdies.
Earlier, Larrazabal and Liang established a one shot lead midway through the first round.
With McGrane heading the chasing pack, US PGA Championship winner YE Yang, fresh from his eighth place finish at the Masters Tournament last week, Finland's Mikko Ilonen and Swede Henrik Stenson sat a further shot off the pace in the clubhouse at four under par.
With older brother and former British Amateur champion Alejandro on the bag, 2008 European Tour rookie of the year Larrazabal, 26, made his move with a "perfect" front nine after picking up five birdies and no bogeys.
The 2008 Open de France champion, who caddied for Alejandro during his British Amateur victory and at the 2002 Open at Muirfield and the 2003 Masters Tournament, eased off for the undulating and bunkered links set up of the back nine and made just two further gains against a solitary bogey.
"I played solid. I didn't sleep too much, only three hours last night as I was suffering a bit from jet lag. So I was up at 1am so when I teed off at 6.40am it felt like 10am so I felt very awake," said Larrazabal.
"I played perfect on the front nine and missed just one putt for birdie. But I missed the drive on the tenth into the bunker. Those bunkers are like links bunkers in Scotland, but I saved par.
"I then missed a five foot putt for birdie at 12 which would have put me at six under. I was not angry but disappointed and then made bogey at 13. I tried to be calm and I made birdie at the next par five then birdied 17 before making a great save at 18."
McGrane finished with three birdies in five holes to head the chasing pack after a bogey-free five under 67 from the 2008 champion.
"I played nicely from start to finish and kept the mistakes off the card," said McGrane, who posted his only European Tour success in Beijing two years ago.
"My short game was good and whenever I hit it close I made the putt. It all added up to a five under par and there was no stress, I just did the right things."