South Korean Park In-Bee's healthy lead has been whittled away by Norway's Suzann Pettersen and could disappear altogether in Pattaya. Photo by Jung Yeon-Je

Bangkok – World number one Park In-Bee is under severe threat of losing the top ranking as she makes a delayed start to the season with her LPGA Thailand title defence from Thursday.

The South Korean has held the top spot for 45 weeks, but her formerly healthy lead has been whittled away by Norway's Suzann Pettersen and could disappear altogether in Pattaya.

Pettersen missed a great opportunity to overhaul Park last week when, needing a strong finish at the Women's Australian Open, she shot a disappointing 80 in her final round.

Park, 25, skipped the year's first two events in the Bahamas and Australia, but she will be hoping her luck holds in Pattaya where she was handed last year's win on a silver platter.

Park was two shots behind Ariya Jutanugarn when she finished her final round, but minutes later the Thai teenager gut-wrenchingly triple-bogeyed the 18th hole to cede the tournament.

It was a stroke of fortune which kicked off an amazing run for Park, who won five more titles including three successive majors in the next few months as she dominated women's golf.

However, she has not managed a win since the US Women's Open in June, and will need to re-assert herself quickly if she is to stay at the top of the rankings.

Park will be acutely aware she is being chased by Pettersen and third-ranked Stacy Lewis of the United States, who have both made it clear that they are after the number one spot.

And she will be anxious to avoid the fate of former world number one Tseng Ya-ni, who spent 109 weeks at the top Ä and won in Thailand in 2011 and 2012 Ä but is now ranked 43rd.

However, Park appeared relaxed about the prospect of defending her ranking and said she had set high goals for the season, hoping to do even better than last year.

“I feel comfortable at the moment. My game is in good shape,” Park told reporters, adding: “I want to do better (this year) than last year.”

The $1.5 million tournament has 17 of the world's top-20 players including world number four Lydia Ko, 16, who is seeking her first win on tour since turning pro in October.

“There has not been as much pressure as I thought there would be,” said Ko of the decision to go professional, which was closely followed in her home country of New Zealand.

“I have been playing okay, which probably helps,” she added.

Australian veteran Karrie Webb, 39, will be on a high after coming from nowhere to win last week's Women's Australian Open, a result which pushed her to seventh in the rankings.

As for last year's runner-up, Ariya, she has only just started playing again after a long spell out with a serious shoulder injury.

Local hopes will more likely rest on Pornanong Phatlum at the par-72 Siam Country Club Old Course. – Sapa-AFP.