The 25 year old, trying to make it five wins in a row by members of Colin Montgomerie's Ryder Cup Team, overtook Paraguay's Fabrizio Zanotti and Swede Christian Nilsson.
Kaymer himself began the run of success by taking his first Major Championship last month.
That was followed by Peter Hanson at the Czech Open, Edoardo Molinari in the Johnnie Walker Championship at Gleneagles and then last Sunday by Miguel Angel Jiménez at the Omega European Masters.
This is Kaymer's first outing since Whistling Straits and if he lifts the €300,000 winner's cheque he will open up a lead of almost €500,000 over Graeme McDowell at the top of The Race to Dubai.
While he is ranked sixth in the Official World Golf Ranking, Zanotti is 279th and Nilsson 255th.
They have only two top-ten finishes between them in 38 European Tour events this season, but shot 65 and 68 respectively to keep their title hopes alive.
It is a big day coming up for both of them. Zanotti is 111th on The Race to Dubai and Nilsson 138th - and only the leading 115 keep their cards at the end of the year.
Zanotti put his improvement down to some hard work paying dividends on the greens.
“I have been putting well all week and that is the main difference for me this week because I have been playing well for a few weeks,” he said.
Nilsson was relieved to return to form, and hopes it has come in time to retain his playing privileges.
“I'm way down on The Order of Merit,” he said. “I had a good start to the season, but didn't play any good after that. It's nice to play well again.”
The forecast is for heavy rain on Sunday and Kaymer's caddie Craig Connolly told him on the 16th that it was important to establish a lead.
"He said maybe we should be more aggressive and I definitely was on the 17th," said Kaymer.
"Then I made one of the best up and downs this week. That was a difficult one with the hump in the green.
"The Ryder Cup was the main goal for this year, but once I reached that I made another one - to win The Order of Merit - and so every tournament is important.
"Once you lead the tournament you should win the tournament, so of course I expect myself to win."
Francesco Molinari and Ross Fisher, the other two Ryder Cup debutants in the field, scored 67 and 68 respectively to be four under and three under.
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