This was my first experience with an onsen spa. As a Canadian, I found the experience, unusual but extremely enjoyable.
The service was very welcoming and helpful to understand the procedures. There were instruction signs as well to help clarify, and many details of the benefits for each step and each bath posted in English.
I found the facility and the experience to be extremely enjoyable, healthy, and will certainly do it again. I have no other facility to compare to, but I have been to some high-end spas in the west, and this experience was among the better.
My friend and I chose a package with a 90 minute massage and spent 90 minutes in the bath area ahead of time. This amount of time was unrushed and about ideal. I believe we paid just under 2000 Thai baht including massage for the overall experience, which I thought was excellent value.
I would certainly return, and will look to enjoy similar onsen facilities when traveling in Bangkok and throughout Asia .