It is the 27-year-old’s second stint at the club, following his previous loan spell towards the end of the 2012/13 season.
“I was really happy with him when he was here before and the work that he did for us,” said Clark.
“I already know the lad and his work ethic and attitude. When he left Bournemouth they were asking for a loan fee which we couldn't do at the time because of financial constraints, but we were always interested in Wes.
“He had a great end to last season with Rotherham and played a huge part in helping them get promoted. I know they wanted to keep him but it wasn't to be and we’re delighted to have him back.”
With Thomas’s addition to the squad, Clark now has three strikers at his disposal, but he says he is still looking to add at least one more forward.
“Wes gives us power, and alongside Matt Green we've got two strikers with really good pace.
“That coupled with Lee Novak, and hopefully one other striker of a different type, it will be a good combination and will give us options at the top end of the pitch.”