Singh, who won the Scottish Open in a play-off on Sunday, was on top of the leaderboard at three-under-par through 11 holes at a benign Royal Lytham and St Annes but dropped three shots over the next two holes.
The two-time Asian Tour number one bounced back with a birdie on 14 but dropped another shot on 17 after finding thick rough with a wayward tee shot.
Still, the Indian star was pleased with his effort, considering he only played six holes in practice after gaining a last-minute ticket into The Open from his Scottish success.
"I played really well the first 11 holes. I think the 13th hole was the hole that got me. I hit a bad shot and I think I got greedy with it. When you hit it in the rough you need to take your medicine and move on. I made a double there but came back with a birdie on the next and made some good pars coming in.
"I think I've just got to stay patient. I'm happy. I've come away with a 70. I thought I could have done much better. But it's alright and I look forward to the next three days," Singh was quoted as saying on Thursday in a media release issued by Asian Tour.
Singh had only a brief look at Royal Lytham and St Annes on Tuesday and then spent several hours at the range on Wednesday. He said he relied on his long-time caddie, Janet Squire, to map out his game plan.
"I take it in a way that if you play a lot of practice rounds, you see a lot of trouble. So you might as well not see it, you might as well just tee it up straight and see the good and go for it. Sometimes it works for me, sometimes it doesn't. I'm still happy. I think it worked for me, and I'm going to do the same most of the time," said the 40-year-old Indian.
"I like to play the golf course blind. I think that's why I paid my dues on No. 13, but that's alright. It could have gone my way, and it couldn't have, too, but that's all right. That's the way I like playing coming into a tournament. I think mentally I was a little tired so I just wanted to take it easy.
"I rely quite a bit on her (Janet), because she's walked the course a few times and I just ask her where to go and just look at the yardage book and fire away."
Singh, whose best finish in a Major was tied ninth in the 2008 PGA Championship, started brilliantly with a 25-foot birdie conversion on the first hole before holing another long effort on the fourth. He snared three more birdies and dropped bogeys on the seventh and 17th holes and a double on 13 where he took two shots out of a greenside bunker.
"I saved a lot of good pars, especially the last hole. Leaves a good taste in the mouth. I think lunch is going to taste good," he said.