Priestland has been capped 34 times by Wales and was first-choice fly-half at the 2011 World Cup, but admits that he is gambling with his international future by moving away from the GUINNESS PRO12.
"I have been at the Scarlets a long time and it's time for a change," he said.
"It's strange to be leaving, but part of life. I have loved my time there and made some great friends. We have had some good wins, some good times and bad times.
"The good times outweigh the bad and I have very fond memories of the GUINNESS PRO12.
"Of course it's better if you are playing in Wales because they get more access to the international team. But if I am playing well at Bath, who knows?
"I sort of knew that when I signed for Bath I would not be doing myself any favours internationally, but I felt as if I needed a different challenge.
"I can't see into the future and what it will mean to me internationally, but I want to play for Wales."
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