The OP, @sqwakvfr, started this topic with the text quoted above, without giving a link to his source.
Just now, I looked the information up on the website of the Thai embassy in Washington DC and found it on this page:
https://washingtondc.thaiembassy.org/en/page/non-oa
The information regarding financial requirements is shown twice, first under the heading "Eligibility", then under the heading "Required documents". These two texts are contradictory and thus confusing and useless.
Eligibility
6. Applicant must have a bank deposit of no less than 800,000 Baht in the last three months or an income certificate (an original copy) with a monthly income of not less than 65,000 Baht, or a deposit account plus a monthly income totaling not less than 800,000 Baht (in one year). In the case of submitting a bank statement, a letter of guarantee from the bank (an original copy) is required
Required documents to upload in the system
4. Recent bank statement showing the applicant's name and ending balance of no less than $30,000 or proof of monthly income of not less than $2,500/month) along with the current bank statement showing incoming income
What shows up in the online application form on the eVisa site, I wonder ?