Can you have a vaccinated Thai guest stay with you during your two weeks in the sandbox.

It's possible if you arrange with the hotel before arrival.

Also you will have to wait for the first test result before they can stay with you.

I saw a, "Can my girlfriend enter Phuket before I get there and join me in quarantine?" question posted in another thread maybe ten days ago.

 

The answer was no.

One of the hotels I was looking at got back to me and yes you can have guests after your first test result about 24 hours after arrival. First 24 hours you are quarantined

I finished my sandbox a week ago. You must remain in the room until the airport test comes back negative (12 hours or so). After that it's just a regular hotel experience like it was in the pre-Covid days - other than a daily stop at reception on my way to breakfast to have my QR code scanned. I had friends come to my room with no issues at my hotel.

 

But just like pre-Covid, different hotels will have different rules about guests/joiners coming to your room. Some are casual about it and others follow the law more precisely and require registration. You'll need to ask at the hotel for their policy. 

I thought it wasn't allowed too but other guests at my hotel are defiantly doing it. I'm not sure what the official policy is as I'd heard before people couldn't have people join them unless married.