Lara, I have heard one video clip where a few transgirls in Thailand spoke and those had alledgedly that procedure done there. It was rather good, but it basically just rumours. There was a transwoman in German television I think last year in the show "transgender" that hat the procedure done with Dr Thomas. Her voice seems to me very weak, feminine but a little bit "gay" - which is more about voice patterns. The weakness was very prominent though, but she had I believe 3 attempts at voice surgery in total, so that may not be the ideal situation either. The voice samples on Dr Thomas' website are mixed as well. As I understand it, if the procedure works, the results are undeniably feminine - but it has a risk of complications that is rather high and it leaves of course a rather big scar.
What I heard recently was, that apparently there is a surgeon in the North of Germany who is doing this procedure as well for some years - but I don't know his name or anyone who has been there. But it may be worth looking into it, if you are from Berlin as your tagline says, this may be an option to get the procedure paid for by insurance (which will not cover Haben or Yeson or Thomas, most likely)