The Thunder kept their BBL season alive on Thursday night with a dominant 57-run win over Hobart Hurricanes in their elimination play-off.

But Hales' fielding at mid-on drew the ire of former Australia captain Ricky Ponting in commentary for Channel Seven.

Ponting said Englishman Hales had broken the rules and wasn't acting in the spirit of the game by stepping outside the inner circle before the bowler had released the ball.

Under fielding regulations, a certain number of fielders must be within the inner circle.

Hales said he had spoken with umpires on the field to clarify what was happening.

"As soon as the bowler lets go of the ball you're allowed to leave the ring, which is what I was doing," Hales said.

"I think that's what they thought on the replay (that I was leaving early) but I was pretty sure I was leaving after he let it go."

Hales said he was trying to anticipate where the batsman would hit the ball.

"If someone goes for a reverse sweep, first slip moves after the ball is let go," he said.

"Once the ball is let go and you see the batsman swing, you can react in the field. For me I think it's fine, if it's in the rules. I don't think it's bad sportsmanship at all."

Hales had earlier top-scored with 60 from 37 balls as the Thunder posted 5-197 at Bellerive Oval.

He shared a century opening stand with Usman Khawaja, who returned to form with 54.

"We've been quite hot and cold actually. For us to click at an important stage of the tournament is good signs," Hales said of the partnership.

Spinner Jono Cook then took 4-21 as the Thunder bowled Hobart out for 140 and progressed to a do-or-die play-off in Adelaide against the Strikers on Saturday.

Australian Associated Press