QB Issue Resolution:

Aside from changing Windows Regional Settings, you’ll need to install Microsoft AppLocale or Locale Emulator to display the Thai language on your software. I’d suggest contacting Microsoft Technical Team for further assistance.

Resolution for Issue 'Why QB Premier 2019 cannot display the Thai language? even though I have used windows 10 display for the Thai language. Every I type the result is just symbols.' available: Yes (Solved).
Source: Intuit Community forum.

Why QB Premier 2019 cannot display the Thai language? even though I have used windows 10 display for the Thai language. Every I type the result is just symbols.: this issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the issue yourself by looking for a resolution described below. If it is a complex issue or you are unable to solve the issue, you may contact us by clicking here or by using other support options.

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