Los Angeles: Legendary trainer Freddie Roach on Tuesday accused Thailand’s Kwanpichit Onesongchaigym of fighting dirty as a world title showdown with Chinese Olympic star Zou Shiming was confirmed in Las Vegas.

Roach, who trains Zou, said he has warned the 35-year-old to beware bruising tactics from Kwanpichit when the two boxers fight for the vacant World Boxing Organization flyweight world title on November 5 in Las Vegas.

Zou has beaten Kwanpichit once before, pummelling the Thai to defeat in a unanimous decision victory in Macau in 2014.

But Roach said Kwanpichit, whose birth name is Prasitak Papoem, had resorted to underhanded tactics en route to that defeat.

“Prasitak may look like Manny Pacquiao but he sure doesn’t fight like him,” Roach said. “He’s dirty as hell.

“The last time we fought him, Prasitak was head butting and landing low blows on Shiming throughout the fight.”

Zou, meanwhile, is dreaming of landing a first-ever professional world crown, having come up short in his previous title tilt against Thailand’s Amnat Ruenroeng in 2015.

“Though my first world title fight was not as successful as I had hoped, I have focused even more on developing and improving myself mentally and physically to meet the challenge of fighting for another world title,” Zou said.

Zou and Kwanpichit’s bout will open an impressive undercard for Pacquiao’s comeback bout against Jessie Vargas at the Thomas and Mack Center, where the WBO welterweight crown will be up for grabs.

Roach, who also trains Pacquiao, said he planned to have Zou spar with the Filipino star as part of his preparations for the bout.

“I’ll have Shiming spar with Manny when we get back from Manila so we’re extra prepared,” Roach said.

Kwanpichit is unfazed by the prospect of meeting Zou again, adamant that he is a vastly improved fighter to the one comprehensively beaten by the 2008 and 2012 Olympic gold medalist two years ago.

“Zou is rated number two and I am rated number three, but that is the only thing that has remained the same from our first fight,” said Kwanpichit.

“I am a much different fighter than the man Zou fought in China two years ago. I have knocked everyone out since that fight and I have developed elephant strength punching power. I look forward to avenging my only loss.”

In another bout confirmed on the card Tuesday, Nonito Donaire of the Philippines will put his WBO junior featherweight crown on the line against Jessie Magdaleno of the United States.

Donaire, 37-3 with 24 knockouts, said he had been working well in training camp under new trainer Esmael Salas.

“We are learning about each other and he’s instructing me on a more precise, compact way of fighting while still being very explosive,” he said.