The Customs Act and the Customs Tariff Decree govern the customs duties. Customs duties are imposed on goods imported and on certain goods exported, including rice, hides, skins and leather, scrap iron or steel, rubber, teak, and other kinds of wood.

Customs duties are collected in accordance with the Harmonized Commodity Description and Coding System (Harmonized System). Thailand has adopted the Protocol Governing the Implementation of the ASEAN Harmonized Tariff Nomenclature (AHTN) to harmonize the tariff nomenclature at the eight-digit level.

Most tariffs are ad valorem, which is a duty laid upon goods at a certain rate, ranging between 5% and 60%, of their value.  However, in certain cases both ad valorem and a specific rate are given, and the higher tariff will apply.
Goods imported for re-export are generally exempted from import duty.
The Petroleum Authority may grant duty reductions or exemptions on certain goods imported by a promoted company or concessionaire.
Duty reductions or exemptions on imported goods may also be granted to members of the ASEAN Free Trade Area (AFTA) and the World Trade Organization (WTO), and to parties of free trade agreements and international agreements to which Thailand is a party (Australia, Chile, India, Japan, New Zealand, Peru).
Thailand is also a member of the General Agreement on Tariffs and Trade (GATT).

Customs duties are imposed on the transaction value of imported goods, which is the price actually paid or payable for the goods when sold for export to the country of importation, plus some costs and charges (royalties and license fees, commission and brokerage, cost of container and packing, design work, that are paid as a condition of sale of the imported goods by the buyer to the seller or by the buyer to a third party to satisfy an obligation of the seller). The invoice value should also include the freight, insurance, and handling charges.
The value of exported goods is based on their FOB (free on board).

Customs Incentive Schemes
To promote Thailand as a global trade hub, certain incentive schemes are available, as following:
•  Tax and Duty Compensation
•  Duty Drawback under Section 19 bis
•  Duty Drawback for Re-Export
•  Bonded Warehouses
•  Free Zone
•  Investment Promotion
•  Gold Card Scheme
•  Licensed Customs Broker
•  Authorizes Economic Operator (AEO)

Customs Controls and Procedures
In general, importers are required to submit an import declaration and supporting documents (a bill of lading, invoice and packing list) via the e-Customs system. In addition, depending on the nature of the imports and regardless of value, the importers may need to obtain a permit or license to facilitate clearance of prohibited or restricted goods (e.g. drugs, medical devices).

Customs duties must be paid upon arrival. However an exemption may apply. Goods priced at 1,500 baht or less that are transported via air freight (through operators such as DHL, UPS, FedEx) do not require payment of customs duties or VAT. In addition, such goods do not require submission of formal import declaration entries with the Customs Department.
Imported goods may be stored in a custom bonded warehouse for no more than 60 days. Before releasing the goods, the importers must pay the landing and storage charges.

All goods being exported from Thailand are subject to customs control and must be reported to Customs. Exporters must submit an export declaration and the required documents via the e-Export system.

Legal Consequences
Non-compliance with customs procedures, false declarations, smuggling, and evasion of customs duties are considered offences and penalties can include imprisonment for up to 10 years, instead of or in addition to the fine.
Import licensing errors and smuggling are subject to fees equal to the multiplied value of the goods.