Happy to Marry

[true66]

I need some help  to how to do the following  in regards to marriage please.

I am an Aust Citizen and want to marry my Thai g/f. Have known each other for over two and a half years. I been to Thai and spent time with her on 3 occasions for about 4 weeks each time.

She has been on a tourist visa  two times 3 months at a time and now she is over here with a tourist visa again for 1 year multiple entries.

After her visa expires our intention is that I go with her to Thailand and get married there.

My queries are:   Am I doing this the best way by marrying over there, then apply for her to get permanent residency for Aust. (intentions to live here). I believe it costs about $7000 for this. Also is it very difficult to fill this application without an agent as agents fee is quite high. If this is ok to do, would she be able to come back to Aust with some other kind of visa and stay till application for her permanent visa is finalized?

I am 68 semi retired and she is 47 if that helps