The Australian marriage/settlement visa is also called a temporary residence permit or a migration visa, and means that you and your Thai partner are already legally married in Thailand before you enter Australia. When your Thai wife is awarded this visa it is for approximately 2 years and allows her to work and obtain free medical care and open bank accounts etc. She will be able to settle in Australia with you as your wife.
After the 2 years in Australia your Thai wife will be given a permanent residence permit to stay in the country for the rest of her life, as long as you can prove that your relationship together is still ongoing and not ceased.
A settlement visa to Australia can be a big move for most foreign nationals including Thais so it is advisable to go for a holiday first to make sure your partner can adjust to the new surroundings.