Jellybean:
I doubt very much that the Thai Immigration department is concerned with the source of your income; my belief is that they are only interested in the monthly amount of your income and that it can be shown to originate from a foreign source. Therefore, as long as your dividend and any other income amounts to at least 65,000 Baht per month, that’s all that will concern them.
From General Information section of Pattaya City Expats Club webpage for Visa & Immigration – Extending Stay (source: http://www.pattayacityexpatsclub.com...endingStay.pdf])

Thai Immigration issued an amendment to order 138-2557 stating the documentary evidence required if the applicant chooses to use monthly income as their financial resource for qualifying extension based on being related to a Thai including marriage (Section 2.18 of each police order) or on retirement in the Kingdom (Section 2.22 of each police order). Thai Immigration issued another supplemental police order35/2561effective March 1, 2019, to change the financial requirements for qualifying for an extension based on retirement.
The Amendment to Police Order 138-2557 shows the following regarding documentation to support use of monthly income (source is copy ThaiVisa.com translation of the order:http://pattayacityexpatsclub.com/exp...1-Jan-2019.pdf)

2.22 Retirement - Document
1. Application form
2. A copy of the applicant’s passport
3. Evidence showing income such as pension or interest received or dividend received and/or;
4. Certification letter from the bank in Thailand and a copy of bank book.
5. In the case of (6), the same documents as described in I - 4 are required.

Item 5 above that refers to item (6) relates to item (6) in the original Police Order to which this amendment applies.

2.22 Retirement - Procedures

Evidence showing income not less than 65,000 baht monthly includes:
1) Evidence showing pension - a letter of certification on deposit in the bank in Thailand and bank statement showing money transfer from overseas every month for the past 12 months. Except in a case where the applicant's retirement is less than 1 year, the evidence must be from the month of retirement. For example, the retirement is started in October 2018, the applicant must show pension payment evidence from November 2018 and pension payment evidence of the whole 12 months is required for the next year or;
2) Income certification certified by the embassy or consular.

As noted, it includes “Evidence showing pension." Based on some recent reports from Jomtien Immigration Office, they are asking to see evidence of the source of the pension/income. They are also requiring a letters from your bank reporting the monthly deposits to the account and verification of the account in addition to copies from the passbook.