I have problem when import items in the Thai language

Usually, the encoding problem appears when you try to open the CSV file in the MS Excel program. Somehow when you simply try to open the file by clicking on it, the new Excel version does not recognize that CSV file has the UTF-8 encoding and open it in another encoding. The sad point is that the Excel does not ask in which encoding to open. Of course, there is the way to open the CSV file in proper encoding. But it is complicated. 

The simplest way is to open the CSV file with Google Sheets.  Here is the guide how to do it: How to Open CSV File in Google Sheets  

Note: This problem appears only with languages that use the alphabet other than Latin. CSV files with content on the Latin alphabet languages have no problem to open in Excel.