The Seiko India website lists the country of origin and manufacturer of individual Seiko models to comply with India’s import laws. None of this is surprising, and mostly just confirms what was already assumed.
Note that this is just the factory the finished product leaves, Seiko Watch Corp. and Seiko Epson Corp both own multiple production sites all over the world, and a large network of third party suppliers, many of which are unknown.
No watches originate from Malaysia or Singapore, though SII and Epson Precision Malaysia both operate watch factories there, presumably making parts, not complete watches.
Summary
China (Guangzhou SII)
- 4R Prospex
- Seiko 5
- 6N quartz
Japan (Morioka SII)
- Almost all presage models (even 2R and 4R ones)
- 6R and 8L Prospex
- King Seiko
Japan (Epson)
- Astron
- A handful of presage with special dials.
Thailand (Epson Precision Thailand)
- Almost all Solar (besides Astron)
- Coutura
- 7N quartz