Hello @Kriangsak Sriban ,
Thank you for reaching Microsoft Support Community.
We would like to have a screenshot of the error received and/or the email address you are using to sign up to perform the respective troubleshooting process and identify what could be the reason for not being able to sign up in azure, however, you can refer to the following article which describes common sing up error/issue scenarios: https://learn.microsoft.com/en-us/azure/cost-management-billing/manage/troubleshoot-azure-sign-up.
If you consider that everything is correct and want to talk with an Azure Subscription Support representative please feel free to create a support ticket here:
I hope this can help you with the facing issue.
Best regards,