Siam Breeze has very good massage therapists.
Unfortunately my favourite one, who was excellent in terms of strength (I like 'hard' massage) and skill (5 stars), left last year and I haven't yet found someone as strong.
But generally they are talented and attentive at Siam Breeze. And the rooms are very pleasant. I always request combination Thai/deep tissue.
This is also the best Thai massage place I've come across in London (I tried a number before deciding c.2018 to come here regularly).