I can weigh in here. I am currently living in northern China with my Thai g/f. She has been here about 3 weeks. I'll be here for at least 2 years and we'll most likely get married. Yes, it's cold (and it's going to be even colder) but she's lived in places before with negative temperatures. My workload is quite heavy as I am at an IB school but I am home at 5 every evening and do a few more hours of work. Before coming here, I let her know what it would be like (the enormous workload) and we researched China and living here so that we were both prepared for what we would face. I believe that we'll be just fine for the next two years and then move somewhere nicer (probably America). It's illegal for her to work here but the apartment is fairly big and modern, there's enough for her to do (besides watching Thai shows via youtube) and together we brought all kinds of ingredients to make Thai food - enough for a year until we visit Thailand again on one of my holidays.
The generalization that Thais will only live in Thailand is complete shit. It completely depends on her and your relationship and how strong it is. There are plenty of Thai people living abroad and are happy doing so. We have always talked about settling somewhere that is not Thailand (neither of us really want to live there for several reasons) so I have no doubt that I won't get the "I miss Thailand and want to go back" scenario.