ทวิภาคี(tá-wí-paa-kee)

bilateral (between two parties/countries)

Involving two sides, parties, or countries; conducted or agreed upon by two entities (e.g., ความตกลงทวิภาคี).

bilateral relations/affairs (as a noun use)

Matters or relations between two countries or parties; often used as a noun in set phrases (e.g., ความสัมพันธ์ทวิภาคี).