I fly in and out all the time for work have lived here since the early 90s. Pre covid was rarely asked by check in staff now i would say I get asked to show visa or ticket about 75 % of the time. Its actually AITA regulations to ask for showing onward flight. In all those hundreds maybe thousands of entries i have been asked to show onward flight by immigration a grand total of 1 times
you get 60 days upon arrival so dont need visa. Where to stay also depends what you want to do Bangkok is big. I personally like IBIS riverside nice clean rooms, great location and good breakfast
Would advise checking here to make sure you have everything needed for your daughter. I think you should be able to get passport at Thai embassy before leaving.
Lots of cases i have read where children need go back get info from embassy where they were born. Just double check they very helpful there.
Yes my wife never had no issues even before we were married, first time she went to UK she came for a weekend for my dads 70th. Met me in UK I was on ship and flew in from trinidad. But she has good job and properties