What ever Visa u want , she would have to leave the UK to apply for it from her ( own or where she resides ) country and comply to all regs. For that Visa.
I have an Asian wife , we had to do the same for a settlement Visa.. she was refused even after previous visits to the UK.
Not easy to get if it was a settlement Visa u sought.
And yes ur right it's not Thailand it's England not the UK.. I can go to Scotland or Ireland ( different rules to England ) and fly out to Thailand but right now I dont see the point.
I will do it in 2022.
My dad is Scottish so I can travel to family and fly out from there.. but not interested right now.