Check th (ไทย) locale and fix typos

Check locales by native and fix typos.

Project use [jekyll-multiple-languages-plugin](https://github.com/kurtsson/jekyll-multiple-languages-plugin). Each locale file are keeped in `_18n` folder.
For example `en` is located in `_18n/en.yml` file.

Project was translated by translation service not by human. So it can keep typos.

Need to check current issue language.

- Fork
- Create branch 186_th_locale
- Commit and create PR

Start by inspecting the Thai locale in the `_18n` folder, using `_18n/en.yml` as the documented example and checking how the Jekyll multiple-languages plugin loads locale files. Review the Thai text for typos, then create the requested branch and submit a pull request with the corrected locale.

Written by the indexing model from the issue text.