WATCH: Two-sport king Regian Eersel sharpens his tools with Burmese legend Aung La N Sang during martial arts cruise

Becoming a combat sports world champion and staying atop that mountain requires dedication of the highest order and ONE Championship star Regian Eersel is wasting no time.

The reigning ONE lightweight two-sport world champion is only a few days away from defending his kickboxing world title against France's Alexis Nicolas in the main event of ONE Fight Night 21 on Friday, April 5.

'The Immortal' has been on an absolute tear for the better part of the past eight years and has produced an astounding 22-fight winning streak along the way, with the hopes of extending it to 23 at the expense of Nicolas.

To better his chances of a successful defense against a surging challenger that possesses pinpoint accuracy, Eersel has enlisted the help of a ONE Championship history-maker.

Second-ever two-division ONE world champion Aung La N Sang held the pads for Eersel to further hone his striking during a recent cruise trip. ONE Championship posted a clip from the training session on its Instagram handle.

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Alexis Nicolas hints at all-out war with Regian Eersel

Fighting for a ONE world championship is not an opportunity that comes every day and Nicolas is out to prove that he can get the upset victory against Regian Eersel.

Nicolas recently stated in an interview with ONE Championship that he has all the respect in the world for the Surinamese-Dutch kickboxing star, but when they do take to the Circle, Eersel should expect nothing less than a back-and-forth war for five rounds.

ONE Fight Night 21 will emanate from the historic Lumpinee Boxing Stadium in Bangkok, Thailand.

The full fight card will air live and for free to all Prime Video subscribers in North America.