docs: update README.th.md for clarity and native-friendly

[BadPROGRMMR]

Update thai translation in readme for readability and native-friendly

Issue for this PR

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

the current translation for README.th.md is alright but very hard for thai native people to read

How did you verify your code works?

i am thai native and i can verify that this change is more readable for thai native

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

Hey! Your PR title Update README.th.md for clarity and native-friendly doesn't follow conventional commit format.

Please update it to start with one of:

• feat: or feat(scope): new feature
• fix: or fix(scope): bug fix
• docs: or docs(scope): documentation changes
• chore: or chore(scope): maintenance tasks
• refactor: or refactor(scope): code refactoring
• test: or test(scope): adding or updating tests

Where scope is the package name (e.g., app, desktop, opencode).

See CONTRIBUTING.md for details.

[github-actions]

Thanks for updating your PR! It now meets our contributing guidelines. 👍