FYI just went to Phuket immigration and they have said that until the plan to extend amnesty visas with an embassy letter has been published in the Royal Gazette they are not able to process 30 day extensions.
EDIT: They also said that the embassy letter must be an original, not a printed out copy from an email.
TLDR : Answer Summary
The situation regarding 30-day visa extensions in Phuket is currently unclear. Immigration officials have stated that they cannot process extensions until a plan regarding amnesty visas, which requires a letter from the embassy, is published in the Royal Gazette. The embassy letter must be original, not a printed copy. Despite various comments suggesting confusion about an extension plan and the publication timing in the Royal Gazette, many have noted differences in practices between immigration offices in Thailand. Some have successfully processed extensions with printed embassy letters, while others have faced strict requirements. Overall, expats are advised to stay updated and possibly wait before attempting to extend their visas.