My Non-O multiple entry visa based on marriage has a Valid Until date of 9th October 2019.

 

If I do a border run on 8th of September and get a further 90 days I will have a permission to stay stamp dated 7th Dec 2019.

 

If I go to the UK on 1st October can I...

 

1) Get a re entry permit at Suvarnabhumi airport that will allow me to come back on my Non-O visa with permission to stay stamp dated 7th Dec 2019?

 

2) Then apply for the one year extension on 7th Nov 2019?

1. Yes

2, Yes 

3 hours ago, STD Warehouse said:

If I do a border run on 8th of September and get a further 90 days I will have a permission to stay stamp dated 7th Dec 2019.

It would be December 6th. The day you enter (8/9) is day 1.

 

3 hours ago, STD Warehouse said:

1) Get a re entry permit at Suvarnabhumi airport that will allow me to come back on my Non-O visa with permission to stay stamp dated 7th Dec 2019?

Yes (6/12). You can also get a Re-entry Permit from your local immigration office anytime between 8/9 and when you go to the UK.

 

Quote

2) Then apply for the one year extension on 7th Nov 2019?

Yes.