I didn't stretch scrotum or anything. I was on a strong anti-androgen, cyproterone acetate and some estradiol and other stuff as well, bicalutamide, progesterone, finasteride. I had my surgery 1 yr and a half later, no problems with depth or surgery.

I also continued taking estrogen (small dose sublingually), progesterone, bicalutamide, finasteride right through surgery as these don't affect clotting to any significant degree. I believe Marci Bowers in the US allows for the continuation of a small dose of bio-identical estradiol until surgery, no stoppage. She is better informed in terms of HRT, she is trans herself.
In Thailand, if you want the honest truth, you don't even need letters for some surgeons. It depends and sometimes, they just have someone from their staff assess you psychologically once and then approve surgery. BUT, I personally think it is important to live fulltime as a woman for a significant amount of time to get an idea if this is what you want, if you feel comfortable with lifestyle, etc.