I don’t have any experience of asking for a Thai to go to the uk ,but it’s not as easy as people are suggesting ,

The paperwork has to be super accurate and I personally do know Scottish people of high financial incomes who have been refused uk visas for their loved ones and its getting worse,

They were all genuine relationships .

They were all way above the minimum financial requirement ,in fact the families I know would have been in the top 5 % of UK earners .

The paperwork is down to interpretation by the officer reading it ,so be prepared to loose money on your application as all applications are non refundable and be prepared for your application to be rejected

But I wish you all the best and hope you do get accepted first time