U.S. Citizen trying to adopt Thai wife's 6 year old daughter

[Siameaze]

I am a U.S. citizen on a Retirement "Visa". I am married since 2013 to a Thai who has a 6 year old daughter. The father left for Europe before the child was born and has not done anything in the way of contact or support. I have known her daughter since she was 9 months old and we are living as a family in Thailand since 2013. I am considering adopting her daughter and would appreciate any guidance on what steps need to be taken.

Reason for considering adoption are varied and range from making school registration easier (too man questions about where is the father), to a sense of legitimacy in a few years when she will probably ask questions, to ensuring continuation of Social Security benefits being paid (after my demise and before my wife reaches 60...a number of years away),

Thanks for any information/direction you can provide

[SantiSuk]

Same question was asked by a Canadian or American a few days ago. Google "thaivisa.com santisuk adopt" or review recent postings on my ThaiV profile to kick off your research.