Starting his round at the tenth, Bachem cancelled out two early birdies with dropped shots at the 14th and 16th before getting firmly back on track with birdie at the 18th.
Another followed at the third and a superb run of four in a row from the fifth completed a front nine of 31 and took Bachem clear of the field.
He credited his short game and said: “My chipping and putting is amazing the first two rounds.
“Yesterday I was hitting the ball so bad, I can’t remember when I hit my irons so bad, but I made every pitch close to the hole, every up and down, holed every putt inside four or five metres, so after the round I was pretty shocked about the seven under!
“Today I felt like I played much better but I didn’t hole all the putts, then on the back nine they went in and it was pretty nice.
“It’s awesome, I was right up there in Kenya two weeks ago (starting 66-67 at the Magical Kenya Open Presented by Absa), it didn’t go how I wanted but I learned a lot (which will put) me in a better position mentally for the next two rounds.”
Langasque made bogey at the second but bounced back in style with an eagle and three birdies in succession.
Further gains at the tenth and 13th and a second eagle of his day at the 16th led to a 64 that left him one behind Bachem.
He said: “It was a good round, 64 today, eight under. Yesterday was actually even better on the long game but I just couldn’t make a putt, today the putting was very solid so that made a big difference.
“This is a golf course where there are so many birdie opportunities. There are a few pin positions where you have to stay away but there are a few par-fives that are playing short, the fairways are quite wide and for me, the biggest thing is the greens are very good and soft so you can be really offensive.
“We know it’s going to be around 20, 22 under to win the tournament, so it’s only halfway and we need to continue in this way.”
He was joined on 12 under by Välimäki, who began his round with three birdies in four holes and repeated the dose over the final four on his way to a seven-under-par 65.
Julien Brun continued his consistent recent form with a 66 featuring four birdies and an eagle at the tenth to put himself among a group of six players sharing fourth place at 11 under.
Ockie Strydom, one of this season’s outstanding performers and fifth on the Race to Dubai Rankings in Partnership with Rolex, joined him by matching Langasque’s 64. The South African’s highlight was a long right-to-left birdie putt at the par-three fifth, while he made six birdies on the back nine including three in a row from the 15th.
Darren Fichardt, who had shared the first-round lead with Vorster at eight under, remained on that mark after a level-par 72.