I believe Fabienne does in-villa massage. She is wonderful!! I've had many massages in my day and she is the best of the best....truly.

http://www.info-res.com/orientmassage/

Here is another place that offers a variety of massage services including treatments of a more personal nature if that's what you're looking for. I've never used them so cannot offer a recommendation.

https://st-maarten-mobile-massage-service.com/