You’re taking about a spuse visa I believe. You need to have 400,000 baht or equivalent in a bank account under your name for 3 months before you apply for the visa. Alternatively proof of income of 40,00 baht per month. You don’t need to keep it there after you have your visa but you need to put it back in 3 months before you apply to renew it eg annually. Obviously doesn’t apply if you can prove regular income of 40k baht per month. Hope this helps.