Then suddenly he bogeyed the third and triple-bogeyed the fourth. The recovery with a birdie on the sixth saw him end the day at four-under which kept him in the lead group at seven-under 137.
But a bogey at the third was followed by a triple bogey seven at the next and he needed a birdie at the sixth to keep pace with the leaders.
European Tour veteran Coles produced the best round of the day, firing a sparkling 65 at the Diamond Country Club.
Coles, whose search for a first European Tour win goes back 15 years and more than 300 events, produced a brilliant seven under par bogey-free round.
Coles came closest to victory at this year's Avantha Masters, where needing a four at the par five closing hole he took four from the edge of the green for a bogey six.
But he had no such problems seeing out his second round here, firing a hat-trick of gains from the sixth -- his 15th -- culminating in a 60-foot birdie putt at the eighth.
He was joined on seven under par first by Luiten, who added a two under 70 to his opening 67.
The quartet are two shots clear of Australia''s Daniel Gaunt, England's Simon Wakefield, Italy's Emanuele Canonica and local amateur Matthias Schwab, who shone with a five-under 67.
PTI