Kiradech Aphibarnrat was left to rue "silly mistakes" after returning an erratic one-over 72 in the first round of the Open Championship.
The Thai ace, who currently leads the Asian Tour Order of Merit, battled back from a bogey at the second with birdies at four and five, and he nailed a 15-foot birdie putt at the 10th to get to two under.
But he paid the price for some wayward iron play on 11, 15 and 16 before parring in, and he admitted Muirfield had provided an immense test for his major championship debut.
"I was in good form but I had a couple of mistakes. You cannot miss your shots on this course. If that happens, then you need to make up-and-downs for par," said Aphibarnrat, who won the Malaysian Open title in March.
"This result is still good for me. I made a couple of easy mistakes so that was a bit disappointing. I just wasn't hitting my irons good enough but my driver and putting raised my game.
"The conditions were quite easy because there weren't much wind. I'm lucky to play early in the morning. That's why I'm quite disappointed I didn't take advantage of the weather.
"But I have a good chance to play on the weekend. I have to focus on my game plan because you need to really concentrate when you are playing on this golf course.
You cannot lose focus because when you do, then the course will punish you."