You must obtain a non immigrant visa entry to extend for retirement so could have saved that 1,900 baht if you had asked earlier. At this point you can run down the 30 day extension at bit and then apply for change of status for a new 2,000 baht fee/TM.86 showing the required money for retirement extension of stay (no requirement for it to be in account any period of time). You get a new entry of 90 days and during the last 30 days present the money again (this time seasoned) and use normal TM.7/1,900 baht fee to obtain retirement extension of stay.
For the same retirement purposes, is it possible to obtain a change of status to a non-immigrant visa, prior to applying for a retirement extension, when in country on a 30 day visa waiver, as opposed to a TV?