Is it possible that sometimes immigration waits to grant the subclass 100 before granting the subclass 309 partner visa?
The 100 might be
granted if you meet the long term relationship criteria. The Department of Home Affairs website defines a long term relationship as:
We consider you have been in a long term relationship, at the time you lodged your application, if you had been with your partner for either:
Three years or more
Two years or more and you and your partner have a dependent child of your relationship.
You will need to provide documents that show you have been in your relationship for this length of time and if applicable, that you have a dependent child.
Do you and your wife meet that criteria? In some cases that we've seen recently, the 100 has been granted to some who may not meet those requirements and we've seen the 309 granted where some meet those requirements.
Perhaps your wife's history of overstaying her previous visa's will play a factor into the Departments decision. I can't say.
My thoughts is that my wife hasnt received her subclass 309 because they are worried that she will not leave the country if the 100 isnt granted.
I'm not sure I understand your logic here. If the s/c 309 is granted she is allowed to stay in Australia until a decision has been made on her s/c 100, as stated on the Department of Home Affairs website
On the temporary 309 visa, you can stay until a decision is made about your permanent Partner visa (subclass 100).
If she is in Bangkok and waiting on a decision, why would the Department be worried about her not leaving the country if a s/c 100 isn't granted? That doesn't make sense.
Why would she leave if she was only granted the provisional s/c 309 and why would the department worry that she will leave if only granted the 309? The 309 (as stated above) allows you to remain in Australia
until a decision is made about your permanent partner visa.
It has been nearly 18 months since the Partner Visa was submitted. She is patiently waiting in Bangkok
Some countries, like Thailand may be considered a "high risk" country and that could be the reason her visa is taking so long to process. It could be in relation to her overstay on two separate visas, it could be because the office processing her application is overloaded. No one can say, really. That said, there could
a chance that at the time of the grant of the s/c 309 that she may get the s/c 100 as well. Don't bank on that, though, just hope for the 309.