Hingis initially claimed her appearance at a low-key tournament in Pattaya next week was a one-off appearance to support the deprived children of Thailand.
The Swiss has since acknowledged that a good performance might well persuade her to return fulltime to the circuit she left, broken in body and spirit, two years ago.
Her retirement aged just 22 ended one of the most spectacular rises and equally dramatic falls in tennis history.
At 16, Hingis was on top of the world, the youngest winner of a grand slam last century, the youngest world number one and the holder of the Australian, Wimbledon and U.S. Open titles.
She compensated for her lack of height with superb court craft, great timing and an indomitable will, a combination which crushed the life out of her opponents. And she did it all with a smile on her face.
At the end of 1997 there appeared little to stop Hingis dominating the game like Martina Navratilova, the woman she was named after, and Steffi Graf before her.
What she had not reckoned on was the Williams sisters.
First Venus, then Serena blew holes in Hingis's game-plan with their huge groundstrokes and her mental strength began to melt down under the onslaught.
DECLINING FORCE
"The game was getting more and more physical, especially when the Williams sisters came in," Hingis said last June.
"I had to up my regime and go and work out, which was not my favourite part."
Hingis won the last of her five grand slam singles titles at the 1999 Australian Open. After winning nine titles in 2000, she became a declining force.
In 2001 she sued Italian sportswear company Sergio Tacchini, saying their shoes had damaged her feet. Operations on her ankles in October 2001 and May 2002 led her to withdraw from the sport. Her last match was in Filderstadt, Germany, in late 2002.
Since then she has been learning English, riding horses and turning up at major tournaments to watch or commentate for television. In Switzerland she advertises
She had resolutely knocked back suggestions she would like to return to tennis, calling it "inconceivable".
In December, however, she announced that she planned to play in Pattaya although a comeback was firmly ruled out.
"That's definitely not something that's on the cards. This is a one-off thing for her. And it fits in well with the charity work she's done in the past," said Lisa Chaffey of Hingis's agents, Octagon, at the time.
Earlier this month, Hingis admitted she was using the tournament as a test of her ability to play fulltime again.
"It will depend on how my body reacts. But one thing is clear -- I still love tennis."
DEPRIVED CHILDREN
Next week the top women will be at the Pan Pacific Open tournament in Tokyo and the leading player in the $170,000 Pattaya event will be France's Marion Bartoli, ranked 39.
After arriving in Thailand on Thursday, Hingis, a goodwill ambassador for the World Health Organisation (WHO), will raise funds for organisations looking after women and children who have suffered abuse and deprivation.
Her reappearance is well-timed for personal reasons and for the good of the game. The Williams sisters are having difficulty regaining their intensity and American Lindsay Davenport, who holds no great fears for Hingis, is currently world number one.
The women's game was overrun by hard-hitting Russians last year and while Maria Sharapova's Wimbledon triumph provided one of 2004's lasting memories, the sport could still do with an injection of Hingis's style and strong opinions.
Certainly her former rivals are looking forward to seeing the "Swiss Miss" across the net again.
"I was really sad and disappointed when she stopped so young and so early," said Davenport. "I've always had a good rivalry and a good friendship with her. I'd like nothing more than to see her back, playing at the top and being competitive."
"I always thought it was sad that she retired in the first place," added Venus Williams at the Australian Open.
"I just think if she can come back and if she can make it, that would be very good for tennis and obviously good for her."
