@Tzidogang

You can download the file from Garmin. Make sure that you have a Garmin GPS model and firmware that supports the Thai TTS voice.
Code:
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Convert to RGN file to VPM file "Thai__Narisa.vpm" by using a HexEditor and delete the first 60 bytes and then save as "Thai__Narisa.vpm".
It's also possible to use as in point 3b from the code section further down in this text.

As with most updates at Garmin. Use "View source" in your Web browser and look for the text comment at the top:
Code:
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And here's the "Thai__Narisa.vpm" file that I have processed according to the description above (~24 MiB compressed to RAR archive):
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