Asking professor for recommendation after rejecting his PhD offer
I don't see any issue at all. Just ask and be honest. What was true in the past may not be true now. You don't need to go into all of the reasons that you refused in the past, but changing your mind about going abroad is not an issue. 

If s/he supported you in the past, they are probably a good person to support you now. Don't let this hesitation work against taking advantage of an opportunity.