I would take her for a 2 month holiday first and see is she adapts to U.K life. You can argue that she'll get a better education in the U.K if you like but if she doesn't attend school and you decide to come back to Thailand it could be difficult to catch up. the danger for me is to do what some of my students have done, country hopping. They end up with their cup half filled. even a tourist visa can be painful tog et so one hurdle at a time.