The same hospital stirred controversy last year for touting a cosmetic procedure called a "3D Vagina" in which the customer's own body fat is used to make genitalia more plump.
The whitening service costs around $650 for five sessions.
"I think it's a good market to enter so we offer the ultimate body treatment to our clients, either men and women," Ms Wattanasiri said.
Whitening and bleaching are not uncommon in other parts of the world and are widely offered online.
But they are particularly sought-after in Thailand, where skin-whitening ads have caused outrage and accusations of racism.
"The obsession ... people nowadays can't embrace their own skin colour," said one Facebook user.
Another user Parin Ruansati posted: "Oh god ... what ever happened to the world?" Another had a lighter response, writing: "why not?".