Hi Sutthipong,
Thank you for your update.
Kindly add/install the required font files to your Linux machine and try the conversion. The reported issue only occurs if the required font is not available in the machine where the conversion take place. However, you can use any other Linux machine (configuration should be similar to your server machine) to check the html file is display properly or not. And please make sure whether the machines are having the same fonts.
Regards,
Gowthamraj K