I really fail to understand why someone would want the need to go through transit, get a security pass just to shower and relax and later go back down to the arrival level considering the pax will be arriving from a F flight, have access to the arrival lounge to do that showering and relaxing and will still have the opportunity prior to the BKK flight to enjoy the F section of the Wing and/or Pier.

For someone who have access to the arrival lounge, the cabanas IMO aren't worth the transit, security pass, back to arrival hall procedure when you will have access to it later anyways for the connecting flight.