Union and Its Territory: Article 4

Article 4 – Laws made under Articles 2 and 3 to provide for the amendment of the first and fourth schedule and supplemental, incidental, and consequential matters.

The Constitution (Article 4) itself declares that laws made under Article 2 and Article 3 are not to be considered as amendments of the Constitution under Article 368.
This means that such laws can be passed by a simple majority and by the ordinary legislative process.

Note –

Exchange of an Indian territory to a foreign country must be done through constitutional amendment under Article 368.
For example – 100th Constitutional Amendment Act (2015) was enacted to give effect to the acquiring of certain territories by India and transfer of certain other territories to Bangladesh in pursuance of the agreement and its protocol entered into between the Governments of India and Bangladesh.