@John *********
pardon me but, IF they are legally married, then one spouse who obtained the DTV Visa can sponsor the other spouse with the same bank account in the amount of 500,000 Thai baht or more. Surely they must read the DTV Visa Application requirements as appear on the Thai Embassy or Consulate website where they will be applying for the DTV Visa.
Read section 5c bottom left column on the DTV Visa graphic.