My Thai wife (US Resident Alien) lives with me in the US. We would like for her sister (in Thailand) to visit and perhaps one day live permanently in the US. She is about 37 YO has two sons which are grown and living on their own within Thailand. My thought is a tourist visa however, it is my understanding it's not just that easy as it is for me to visit Thailand as a tourist. Can anyone give me some positive advise on steps we need to start the process. We have money and a residence here in the US to support her for a 30 day type visit.

US immigration laws presume that every visa applicant is an intending immigrant to the USA. Your wife's sister will have to overcome this presumption in order to qualify for a visa. Briefly, that means that she must show that she has reason to return to Thailand. That can be shown in many forms, eg a job, family, property, savings, etc. If she cannot convince the visa officer that she has incentive to return to Thailand, then the visa is likely to be refused.

If you are acting as sponsor, then your situation and support will be taken onto account. However, it is likely that the visa officer will have no problem with your sponsorship and he will be concentrating on your sister in law's reasons to return to Thailand.