It's difficult to tell exactly which of the two options the OP is asking about. Here's my experience:

1. There's a place called The King and I across the street from the Westin. Very very nice, though not opulent. I got a one-hour foot massage from a very funny and charming girl and then a one-hour Thai massage for 12EUR total. This place was recommended to my by SanDiego1K.

2. There is a place called Adonis Massage I think further up Sukhumvit Rd. The taxi driver will know where. It was recommended to me by a different FTer, who shall remain nameless. While I did not partake, it is my understanding that a massage with happy ending will also run about 6EUR for the hour, plus an obligatory 6EUR tip (whether your ending is happy or not).