Welcome to CiviCRM!
You can get an up to date civicrm.mo for Thai at this address:https://download.civicrm.org/civicrm-l10n-core/mo/th_TH/civicrm.mo
This file is recompiled every day using the strings from Transifex (https://www.transifex.com/civicrm/civicrm/language/th_TH/
). So you can improve the translation on Transifex, wait a day, and update your translation file.
For a short term solution, I have generated the MySQL files for you: https://bidon.ca/files/tmp/civicrm-th_TH.tar.gz
These files work on the latest 4.6.10. You can copy them to your "sql" directory of civicrm.
To generate the sql files, normally you would have to configure a CiviCRM development environment:http://wiki.civicrm.org/confluence/display/CRMDOC/Contributing+to+CiviCRM+using+GitHub
Once you have CiviCRM installed from Git, you have to place the civicrm.mo file in l10n/th_TH/LC_MESSAGES/civicrm.mo (similar to other files in the civicrm-l10n.tar.gz file), then run bin/setup.sh (needs to be configured first, depending on whether buildkit or gitify took care of that).However
, writing this makes me realize how complicated it is, just for translation files. Also, the development files for CiviCRM are very big: 500-800 megs total.
Alternative: you can install CiviCRM in English, then change the language after the installation is completed (in Administer -> Localisation -> Language). The main reason to install CiviCRM in Thai directly, is that many configurations are translated, such as "name prefixes" (Mr, Ms, Dr, etc), "phone types", "location types". However, you can also change those after the installation, from the administration menus. Considering that currently the Thai translation is only at 5%, not many configurations are probably already translated. If you can help improve that in Transifex, it would be great, to help the next person who will install CiviCRM in Thai.
If you can help improve the Thai translation and get it around 20% on Transifex, we can include it in the supported languages, so that it gets included in civicrm-l10n.tar.gz. This way, the .sql files gets auto-generated in the next release and it is much easier.
If you have any questions, please do not hesitate to ask on this forum.