Which immigration office in Bangkok should I visit for my visa extension, and when does the extension start?

The user is seeking advice on which immigration office to visit in Bangkok for a visa extension and whether the extension starts from the application date or from the last day of their initial 30-day entry. Comments indicate that visa-exempt entries (30 days) should go to Muang Tong Thani and that the extension will start from the date of application, which means early applications do not negatively impact the visa duration.