Ed visa - new rules.
Previously at the end of your Ed visa(360 days), you had your visa, date stamped with the date you are leaving Thailand, free of charge.
I have been advised new rules state that at the end of your last 90 day extension(360th day), you must pay 1900 baht for a 7 day extension , before leaving Thailand on the same date your Ed visa was stamped upon entering Thailand the previous year.
The attached doc dated October 2018, from Thai embassy in Laos states 1 Ed visa per calendar year.
TLDR : Answer Summary
New regulations for the Ed visa in Thailand state that upon the completion of a 360-day period, applicants are now required to pay a fee of 1900 baht for a 7-day extension. This adjustment means that instead of receiving an extension free of charge, as was previously the case, the 7-day extension must be procured at the end of the last 90-day extension. According to documentation from the Thai embassy in Laos dated October 2018, only one Ed visa is permitted per calendar year.