Wales take on the south sea islanders who have built up a fearsome reputation for their physical approach to the game with their no holds bared approach
But Wales prop Thomas, who certainly packs a punch himself at 6ft 1in and 18-stone, insists Steve Hansen's men will be up to the challenge.
"We already know only too well how the Tongans like to play and that they love the physical approach to the game," he said.
"They are a big powerful team full of natural athletes who look to impose themselves on the opposition with big hits. Sometimes it seems as though their priority is taking the man rather than playing with the ball.
"So we will have to have our wits about us if we are going to win but you can't shirk away from the battle ahead or sit back and take it all, you have to front up and meet fire with fire."
Tonga's reputation appeared well founded in their opening game of the World Cup against Italy on Wednesday when they had two players shown yellow cards including flanker Ipolito Fenukitau for a late and dangerous tackle after just 90 seconds.
That 36-12 defeat to Italy has upped the stakes for Tonga ahead of the clash with Wales as all three teams and Canada fight for one of the two qualification spots for the quarter-finals with favourites New Zealand.
Meanwhile Wales are full of confidence after their 41-10 victory over Canada but are well aware that they cannot afford to slip up with the All Blacks still to come.