Pornanong Phatlum put her miserable Women's British Open record behind her on Friday, hitting a second successive 67 to lead by a single stroke at the halfway point.
In her first seven appearances at the tournament the Thai player made just a single cut but the turnaround at Royal Lytham and St Annes has been dramatic.
The 28-year-old has completed 36 holes without one bogey and is the leader on 10-under par.
Pornanong is one shot clear of group of three players -- England's Georgia Hall, Japan's Mamiko Higa and the first-round leader, Australia's Minjee Lee.
"If someone had told me I was going to go 67, 67 I would have thought 'wow'," said Pornanong.
"I have always found links courses really hard," admitted the player who finished tied-27th when she did make the cut at Royal Birkdale in 2014.
"This is my first time at Lytham and I've played really well, managed to stay out of trouble and my putting was very good. I am so happy. But now I am going to rest tonight, watch some Thai dramas and try and stay relaxed."
Pornanong, a 16-time winner on tours in Thailand, Asia and Europe, admits she has been inspired by the Jutanugarn sisters -- Moriya and world number one Ariya -- who have boosted women's golf in her home country. Ariya won this title at Woburn two years ago.
"They have both won on the LPGA Tour," she said. "It has made us all think that we can do it too. A lot of girls are now playing golf in Thailand. I got it into because of my Dad -- he is golf crazy."
- Not the longest hitter -
Slight of build, Pornanong is not the longest hitter. But she packed five woods into her bag and plotted her way to birdies at the fourth, sixth, seventh, 10th and 16th holes in her flawless second round.
Australia's Lee looked set to retain her overnight lead but a double-bogey -- she went from one greenside bunker to another -- at the 16th and a bogey at the 17th left her having to settle for a 70 and a nine-under total.
Hall, with a second-round 68, matched Pornanong's feat of negotiating two rounds without a bogey.
"That's my longest streak ever without dropping a shot," said the delighted 22-year-old, who is aiming to become the first British winner since Catriona Matthew at Lytham in 2009.
Matthew is not out of it. The 48-year-old Scot moved to three-under-par after a second-round 70 that included a chip-in eagle at the 15th and a holed bunker shot for a birdie at the last.
Ariya Jutanugarn was also on three-under-par following a 70, and Kim In-kyung, the defending champion, was on the same mark.
A golden run of birdie-eagle-birdie from hole five helped Higa to a 69 and the share of second place. "These three holes were the key today," she admitted. "I feel really good going into the weekend."
Canada's Brooke Henderson had a hole-in-one at the ninth -- Florentyna Parker had an ace at the same hole in round one - and shot a 70 for five-under.
The cut fell on one over par and those that missed out included Evian champion Anna Nordqvist and 2015 British Open champion Park Inbee.
The only amateur to make the cut was Thailand's Atthaya Thitikul after the 15-year-old shot 71 for level par to assure herself of winning the Smyth Salver.
Thailand's Pornanong Phatlum watches her shot to the 18th green in the second round of the Women's British Open