When can my husband apply for a 1-year extension based on marriage with a non-O visa?

The earliest your husband can apply for a 1-year extension based on marriage (non-O visa) is 45 days before the current entry stamp expires on 30 April. It is recommended to prepare for the extension application at least 30 days prior to this date. Additionally, ensure that the required funds of 400,000 THB have been maintained in the bank account for at least 2 months before submitting the application.