Thanks guys for all your input but my original question is still unanswered: "I would need an expert to come to my house and give some advice. "
In other words: Does anyone know of an IT expert here in Hua Hin who could come to my house?
Yes, I have a 3BB Internet connection. The installed Wi Fi extenders are not sufficient to cover all rooms in my house. I believe to just buy another extender is not the solution. I would not an expert to come to my house and give some advice.