Thai immigration in Nakhonsawan is where you report your 90 days stay in Thailand. You can also extend you visa such as a tourist visa or a marriage visa for Thailand or Thai retirement visa while in Thailand. You can also speak to them about permanent residency in Thailand.
The the map below as well as the contact numbers for the immigration office. The telephone number, map an email address and also their opening hours. Note that the immigration office is near the tourist police offices in Nakhon Sawan.
Thai Immigration Nakhon Sawan
No. 399 Moo 9, Garden Way. T. Nakhonsawantok District Nakhon Sawan
Phone: 0-5688-1517-8 / 0-5688-1518
Opening Hours: 8:30am-4:30pm Monday to Friday
Service Area: Provinces of Nakhon Sawan, Kamphaeng Phet, Uthai Thani