Heather Watson battles into quarter-finals of Thailand Open

The British number six will climb back into the world's top 150 following a 6-3 5-7 6-4 victory over Han Na-lae that lasted two hours and 33 minutes.

Watson, 30, led by a set and a double break before her South Korean opponent found her range and hit back to force a decider.

A break ahead in the final set, Watson hurled her racket in frustration after being pinned back to 4-4.

But she regained her composure to break once more and then finished the job with a superb drop shot on her second match point.

"It was a really, really tough match," said Watson. "It was actually a bit shorter than my first match, but it felt a lot longer because the conditions were really tough, it was very humid. It was just a real physical battle out there.

"I think tennis went out the window and it was just survival of the fittest. And I'm just really pleased I could get over the line and serve out when it mattered."

Watson will face Chinese seventh seed Wang Xinyu, the world number 81, in the last eight.

"I haven't played her before, but I've practised with her. She's a lovely girl, we get on really well," added Watson.

"She hits a big ball so I'll have to be feeling physically good tomorrow because I have to be quick off the mark."