Add BOI investment promotion strategy

Group B base activity (plastics) with non-tax package and machinery duty
exemption; CIT value engineered via solar/BESS, smart-and-sustainable
automation, and R&D merit measures; NEC/Lamphun regional angle; BOI
approval sequenced ahead of incorporation and machinery orders

README.md

@@ -67,6 +67,10 @@ The detail lives in dedicated documents:
   commitment, and the materials strategy
 - [Worker safety](docs/worker-safety.md): safety training, galvanics clean
   rooms and decontamination, PPE
+- [BOI investment promotion](docs/boi.md): the promotion strategy (Group B
+  base activity plus solar, automation, and R&D measures for the tax value),
+  requirements, Northern-region angle, and why BOI approval precedes
+  machinery orders
 - [Facility security and site systems](docs/facility-security.md): access
   control, CCTV, whole-factory HVAC (temperature, humidity, PM), archive and
   audio protection, fire and life safety, plant monitoring, Thai compliance
@@ -93,6 +97,7 @@ docs/
 │   └── pressing-line.md   Press fleet strategy and equipment plan
 ├── finance/               Project cost overviews
 ├── suppliers/             Supplier contacts, vendor landscape, supplier map
+├── boi.md                 BOI promotion strategy and requirements
 ├── facility-security.md   Security, HVAC, fire and life safety, compliance
 ├── process-flow.md        Audio file to delivered record, with all checks
 ├── quality-automation.md  Stamper metrology and layered record QC