This is for 12 month permision to stay.
2.18 In the case of being a family member of a Thai national (applicable only to parents, spouse, children, adopted children, or spouse’s children): Each permission shall be granted for no more than one year.
(1) The alien must have been granted a non-immigrant visa (NON-IM). (2) The alien must have proof of relationship. (3) In the case of spouse, the relationship must be de jure and de facto: or (4) In the case of children, adopted children, or spouse's children, said children, adopted children, or spouse's children must not be married, must live with the alien as part of the family, and must not be over 20 years of age except in case of the person hereof is of illness or disability and cannot live without support of father or mother: (5) In the case of parents, the father or mother must maintain an average annual income of no less than Baht 40,000 per month throughout the year or must have deposited funds of no less than Baht 400,000 to cover expenses for one year. In case the father of mother requests to be under maintenance of children, the age of father or mother must be 50 years of age or over. For other necessary cases, the Commissioner or Deputy Commissioner of Immigration Bureau is granted the authority to make decisions regarding approval on a case-by-case basis