To achieve "complete HS code change" (i.e. meeting the tariff code change requirements of the rules of origin, CTC) for product components after production in Thailand, the core is to ensure that the processing carried out in Thailand meets the "substantial change" standard - that is, the first 4 (or 6) digits of the HS code for the final product must be different from the first few digits of the HS code for all major raw materials/components imported from non ASEAN countries (such as Japan, South Korea, the United States, and Europe).

01· Clarify the HS codes of raw materials and finished products;    

Taking metal parts as an example

Confirm HS code for imported raw materials/components:
For example, when importing cold-rolled steel plates from Japan, the HS code may be 7210.xx (Chapter 72: Steel).

Confirm the HS code of the final metal component:
For example, after processing in Thailand, it becomes a metal bracket for automobiles → HS code may be 8302.xx (Chapter 83: Miscellaneous Products of Base Metals).

Key comparison:

Raw material code: 72.10

Finished product code: 83.02
→ The first two digits have changed from "72" to "83", which is a chapter change (CC) and meets CTC requirements!

02· Choose a processing method that can "completely change the essence of the product"

Common operations that comply with CTC in metal processing:

  Processing that does not comply with CTC (tax number unchanged):

Imported Japanese steel plate (72.10) → Cut only according to size (still 72.10)
Imported Chinese castings (73.25) → Simple spray painting for rust prevention (still 73.25)
Imported German bearings (84.82) → assembled with other parts into equipment (if the finished product still belongs to 84.82)

03· Ensure sufficient processing depth (avoid "micro processing")

Qualified operation	Unqualified operation
▶ Casting/Forging (Blank → Complex Shape)	▶ Simple cutting and polishing
▶ Stamping/bending (flat plate → 3D structural component)	▶ Apply anti rust oil and label
▶ Welding/riveting (combining multiple parts into a new component)	▶ Sorting and packaging
▶ Heat treatment (changing metal properties)
▶ Precision machining (turning, milling, drilling complex parts)
▶ Surface treatment (electroplating, spraying) needs to be combined with other processes

Surface treatment alone is usually not enough!
For example, imported Japanese screws (73.18) are still screws (73.18) after electroplating in Thailand, with the same tax number.
However, if electroplating is a part of the "stamping+electroplating+assembly" process and the final product tax number changes (such as becoming 83.02), then the overall requirements are met.

04· Avoid the trap of "mixed processing"
Problem scenario:

Imported metal bracket from China (HS 8302)+imported screws from Japan (HS 7318)
>In Thailand, screw and assemble onto the bracket → The finished product is still the bracket (HS 8302).
Result:

The bracket (8302) is consistent with Chinese raw material HS → compliant with rules (China is a free trade partner).
The first four positions of the screw (7318 → 8302) are different (73 → 83) → comply with the rules.
✅ Overall compliance!

Trap scene:
Imported precision gears from Japan (HS 8483)+locally produced casings in Thailand

→ Assemble the reducer in Thailand → The finished product belongs to HS 8483.

Result:
Gear (8483) has the same first four digits as the finished product (8483) → Does not comply with CTC rules!
❌ RVC rules or low content rules need to be used instead.

Summary               

How to ensure a complete HS change?
Choose the right processing method:
Physical/chemical property changes>Morphological changes>Simple processing.
(e.g. casting+machining>cutting+bending>sandblasting)

Aim for tax ID "jump seal":
Focus on making the finished product leave the HS seal (first two digits) to which the raw materials belong.
(Example: Steel (Chapter 72) → Machine Parts (Chapter 84), Auto Parts (Chapter 87), Furniture (Chapter 94))

Retain processing evidence:
Production process records (including process diagrams and working hours);
Mold/equipment photo;
Comparison diagram of raw materials and finished products (reflecting changes in form/function).

Pre categorization:

Apply for HS pre ruling with Thai customs or declaration agency, confirm the tax numbers of raw materials and finished products, and avoid disputes!