If u didnt marry.Take birth certificate from local amphur also adress certificate.And if u can have copy id of your child take it.If possible take wife id card copy.And go to Savannakhet Embassy in Laos.Your visa will be 3months Non O dependant child.Then come back Thailand enter with it.After that before expiry 1 month if possible u must go to Amphur together with your child and wife.Then take that document from there.Go to Immigration.You can choose 2 options 1: 2 more months extension no need bank statement 400K thai baht 1900 baht pay u get 2months. 2: If there is 2 months before apply 400K in your bank account.U can get 12 months.
i saw officer asked to a japanese man.He couldnt show.And he looked like didnt understand officer.Then officer rejected him.Probably statement was fake.Officer didnt believe him