@apremgeorge I stumbled across your; post how to write csv in r where data is cleaned with UTF-8 characters? while trying to export a dataframe with Arabic letters. My issue was that the Arabic letters would not display properly when I opened my exported .csv file in Excel with.
Building on nwerth's first answer, I think you might be able to use
write_excel_csv() rather than
write_csv to get the Thai to display correctly
readr::write_excel_csv(data_df, file = "data_df.csv")
You may want to try this function to see if it better preserves the encoding. Good luck!