Sorry not a Thai but Vietnamese for a restaurant I'm involved in. We used an agent in London to do the paperwork for a fixed fee of £900.
To be honest, we knew who we wanted to bring over, a couple of fairly low qualified chef's and it was fairly painless
We guaranteed a salary of 32k each and advertised everywhere for the right people. We deduct their housing costs, utility costs etc etc. We also deduct the costs of their flights. All fairly easy.
I would imagine the fact that it is a Thai would be more problematic as their are plenty here that can do massage, chef work, translator etc.
You basically have to show that no one here can do the job or no one here wants the job. As for personal questions, I'm not sure what you mean. From what I remember, it is the same questions for an individual as it is for a company.
The agent we used said after that they can get 'family visas' very easy and they can work should we know any family members looking to come to the UK. (one of the directors is a Viet chef)
It appears you may be located in Dumfriesshire, maybe not so many Thais down there but I seriously don't think you would get a WV for a kitchen helper. I would describe it as a 'specialised Som Tam chef' able to speak fluent Thai.
Personally, like yourself I couldn't be bothered with worrying and handed it to an agent.