* Thompson loses playoff to Korean Ryu
* Rules breach on Saturday costs her four shots (Updates after playoff)
April 2 (Reuters) - A tearful Lexi Thompson credited her caddy and fans for helping her get through an emotional roller coaster in the final round of the ANA Inspiration on Sunday after she was hit with a four-shot penalty then lost in a playoff for the title.
Thompson had been leading by three and walking to the 13th tee with her second major title in sight when she was stopped dead in her tracks by a rules official, who told her of the penalty.
A television viewer had alerted the LPGA on Sunday that the American had marked her ball then replaced it in the wrong place on the 17th hole a day earlier, which cost her two shots for the breach and another two for signing an incorrect scorecard.
Thompson was incredulous after being notified.
"Is this a joke?" she said. "Oh my God. Four-stroke penalty, that's just ridiculous."
The 22-year-old gathered herself and had an eagle putt to win on the last, but settled for birdie to force the playoff against Ryu, with both locked at 14-under 274.
The South Korean then took the title with a birdie at the first extra hole.
A devastated Thompson said she would learn from the incident, which prompted an outpouring of sympathy around the golfing world.
"My caddy helped me out tremendously," she said in a televised interview. "He said 'Stay with it, you can still win. We can birdie this hole,' and I tried to gather myself before I hit the tee shot."
Thompson, who won her only major at the same event in 2014, said she was proud of the way she battled back.
"It's great to have the fan base I do. They got me through the whole round," she said. "It's unfortunate what happened. I did not mean that. I fought strong to the finish and it was great to see the fans behind me."
The LPGA said they had been compelled to investigate the incident after it had been pointed out to them.
"On Sunday afternoon, the LPGA received an email from a television viewer that Lexi Thompson did not properly replace her ball prior to putting out on the 17th hole during Saturday's third round of the ANA Inspiration," it said in a statement.
It added that after a full review it informed the player of the four-stroke penalty as she walked to the 13th hole.
Her playing partner Suzann Pettersen said she knew there was a problem right away when the rules officials came out, and praised Thompson for keeping her cool.
"For her to come back with those birdies shows the character she is," she said. "I have got goose bumps."
Tiger Woods led the chorus of golfers calling for television viewers not to allowed to influence a tournament.
"Viewers at home should not be officials wearing stripes," he said on Twitter.
Brittany Lincicome, who won the ANA in 2009 and 2015, said: "We really need to do something about people being able to call in. Especially days later."
Zach Johnson, Masters champion in 2007 and the 2015 British Open winner, said Thompson showed the, "Heart of a champion" and added "... some things in sports just don't make sense".
The incident follows similar rules controversies at the men's and women's U.S. Opens last year, when Dustin Johnson and Anna Nordqvist were both assessed penalties after officials reviewed incidents recorded on television.
Writing by Peter Rutherford in Seoul; Editing by Greg Stutchbury