For a visa from the US my girlfriend had to write a letter of invitation....it was in English. She signed and scanned a copy with her Thai ID with it. Never had an issue on that.
Depends on where you going and where you're staying. If you're staying in the common places that most people like to visit it's very easy to get a ride from one place to another and pull your wheel luggage to wherever you got to go. If you're staying more rural it might be more difficult to drag your luggage and be easier to carry it on your back.
of course Thailand welcomes US citizens....they bring tourist money. If the US welcomed every poor Thai girl they would have the same problem with Thais as they do with poor Mexicans and South Americans living there illegally and still somehow getting all the social programs for poor people. at a cost of approximately $150Billion USD per year. I'm curious as to how much Russia provides to illegal aliens per year? There are an estimated 11.4 million unauthorized immigrants living in the United States.....how many are there in Russia?