For the 90 day extension of stay based on STV, you will submit the following documents found in the attached e-mail. You will go to Changwattana Immigration Office for that service.
For the TM 30, in Bangkok, you can self file at the Muang Thong Thani immigration office. You will need the following documents:
Self filing a TM. 30 requires the following documents:
1. The passport and a copy of:
a. The data “picture” page
b. The most recent visa (if applicable).
c. All entry stamps or extension of stays (if applicable) since arrival
d. The departure card (“TM 6”) that should be stapled in the passport.
2. The original and one copy of the lease.
3. A completed TM. 30 form filled out as follows:
a. The foreigner’s name is completed on the top form
b. The foreigner’s current address is written in both address spaces.
c. On the second page, the table, complete as normal.
The TM30 paperwork can be found in the office.
Easiest way to get to both immigration offices is BTS to Wat Phra Sri Mahathat station, then get a cab from the roundabout under the station.