This thesis will primarily cover the meaning of the “breach” together with the “Seller’s remedies in regard to the Buyers breach of the contract” which states under the United Nations Convention on Contracts for the International Sale of Goods (hereafter “CISG”). Under the scope of the CISG, breaching of contract means one party fails to perform his/her obligations as states in the contract, so the purpose of Article 25 CISG provides a concept of the “breach” which leads to the aggrieved party to avoid the contract (Article 72 CISG) and Article 49 and 64 governs the right of an aggrieved party (A) to avoid the contract when the other party (B) has committed a breach of contract by defective performance or by failing to perform by the date required under the contract. Due to there are 2 types of breaches such as (a) fundamental breach and (b) anticipatory breach but the aggrieved party can only claim for the recovery when the other party committed to the “fundamental breach”. So in the case of breaching of contract by the buyer, in which extend the seller can claim for it, the thesis provides both theory and practical methods in order to find out the simple way to understand about CISG, for following aspects: what are the defining rules in term of fundamental breach and remedies for both parties and the seller especially, how do the courts consider in term of the breach and how are the matters solved. But, this thesis focuses not only CISG itself but also provides some rules in term of breach and remedies from contract and tort law of another continent as Lao PDR, which just accedes to CISG lately on 25 September 2019.