As mentioned above, the sauna is in Rama IX Soi 49, just within the first sub-soi on the right. It is well-marked and easy to find.

I cannot give advice on public transport, as I drive. But Rama IX Soi 49 is on the portion of Rama IX between Ramkhamhaeng Road and Srinakarin Road. Soi 49 is on the north side of the street, past the Premier entertainment complex.

If you want to take a taxi, just say "Thanon Pra Ram Kao, Soi See-sip Kao" and you will get there. Just get off right when the taxi goes into the soi, then look for the "Falcon" sign on your right.