You are reading it wrong.
The relevant section is 2.18 (5)
Everything else is irrelevant and nothing to do with what is being discussed.
(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. 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.