You husband has to apply on his own then once accepted he can apply for the whole family doing it in Malaysia is not a good idea many applicants have been refused they don’t have to give a reason why
You need to get a 90 day non O visa from a thai embassy or consulate outside of Thailand this will allow you to open a Thai bank account and get a 1 year extension if you don’t use an agent you need to have 800k in a thai bank account for two months prior to applying