The Amata Spring Country Club in Thailand had proved a happy hunting ground for Guan, who won the Asia-Pacific Amateur Championship there in November to seal a place at the Masters in April.
He returned to the course eyeing one of the four spots for the July 18-21 Open at Muirfield, Scotland but might have already missed the bus after opening the two-day qualifying tournament with a one-over-par 73.
Guan stumbled on his front nine, dropping a shot on each of the last three holes, and the couple of birdies on the amateur's way back could not fully offset the damage.
Bangladesh's Siddikur remained on course to become the first player to represent his country in golf's oldest Major after sharing the opening round lead with Japanese amateur Hideki Matsuyama on six-under-par 66.
Siddikur was in a similar position in 2011 but was disqualified on the final day after failing to write down a score for the last hole.
Matsuyama was also out to avoid a repeat of 2012 heartbreak. The Japanese dropped six shots in the final three holes last year to miss the playoff for the fourth Open place.
"I've forgotten about that and have already moved on," the promising Japanese said .
"I'm looking forward to the last day and if I can keep playing like how I did, then I'll be able to earn a place."
China's Hu Mu, Australian Scott Barr and Singaporeans Quincy Quek and Lam Zhiqun were a further shot back in a tie for third, with another amateur, Taiwan's Pan Cheng-tsung, in a group at four-under.