I am not sure it works that way, but I will be thinking another thing. What if, as an engagement gift, if you want, Lara takes Raith to the island so Thomas can feed from him, killing him. It would be a fitting end for the man that killed Thomas (and Harry's) mom. And then, with Thomas "a little better", Lara (well fed herself) could pass some of her energy to Thomas.
That way, Thomas will recover and I am sure they can manage to have Thomas back to Lara's place without anyone noticing. He could even feed for some humans there without killing them until he recovers his health.
At this point, I believe everyone knows that Lara is the actual Queen, so no one would care if Raith is off.
Another thing about Thomas, for now, he is bound to Harry. Which is hilarious considering that several characters considered that Harry was Thomas' thrall.