If you can't get a primary letter from a LICENSED Psychologist or Psychiatrist AND a 2nd support letter from a LICENSED psychologist, Psychiatrist, sexologist, or gender therapist then you can choose to have Dr Chettawut/Ms Som consult you with 2 therapist in Thailand but that will be more expensive as she told me.
I got a primary letter from a Licensed psychologist with the letter addressing it to Dr Chettawut with the WPATH guidelines included in the letter as well as a signature and the license number. If they have a website and a business card, that would help out Dr Chettawut and his team extremely so they can determine the authentication of the licensed psychologist, etc.
Once you send a copy to Ms Som, they will let you know by email if it is approved by Dr Chettawut. Once it's approved, just make sure you keep the original files in a safe place cause Dr will need that when you have your consultation when you get to Thailand