Hello @Tetsuji Morita
We recommend all the thin client vendors to reach out via your Microsoft Partner/Account team. Looking at your website, we see you offer your devices with Windows 10 IoT enterprise and proprietary Linux flavor. The Windows-based devices should be ready today to connect to AVD/W365 using Windows App or MSRDC.
If I have answered your question, please accept this as answer as a token of appreciation.