Can my fully vaccinated Thai girlfriend join me in the Koh Samui sandbox program in December?

I am trying to find information regarding the Koh Samui sandbox program and whether it allows people living in Thailand to also get into the sandbox (if they already have their 2 vaccines).

Here is a bit more context about my inquiry:

1. I am Canadian and am fully vaccinated (AZ).

2. I am planning a trip in December, and understand that the first week I will have to stay in one of the SHA Plus Extra hotels on Koh Samui.

3. I am already familiar with the COE requirements (PCR, insurance, prepaying hotel, etc...).

My question is whether my Thai girlfriend (who lives in Bangkok and is also fully vaccinated) can come and joine me in Koh Samui. I understand that right now this would be impossible, because all domestic flights had been cancelled. However, it seems that this restriction will be lifted in September.

I have searched in this group and also online but I haven't been able to answer this question. I also reached out to some of the hotels and online agencies but the answers I got were not entirely clear. The response was along the line of "It should be OK, but we're not sure". Is anyone aware of any official government policy (TAT) on this?

Thanks for your help!