Passage: The Kra Isthmus (Thai: คอคอดกระ, pronounced [kʰɔ̄ː kʰɔ̂ːt kràʔ]; Malay: Segenting Kra/Segenting Kera) is the narrowest part of the Malay Peninsula, in southern Thailand.The western part of the isthmus belongs to Ranong Province and the eastern part to Chumphon Province, both in Thailand. The isthmus is bordered to the west by the Andaman Sea and to the east by the Gulf of Thailand.The Kra Isthmus marks the boundary between two sections of the central cordillera, the mountain chain which runs from Tibet through  the Malay peninsula. The southern part is called the Phuket chain, which is a continuation of the greater Tenasserim range, extending further northwards for over 400 km (250 mi) beyond the Three Pagodas Pass.On 8 December 1941 local time, the Imperial Japanese Army landed near Songkhla, Thailand and Kota Bharu, Malaya, thus beginning the Pacific War, and launching both the invasion of Thailand and the Malayan campaign, the latter of which culminated in the capture of Singapore.The Thai Canal is a proposal to join the Gulf of Thailand with the Andaman Sea. It was originally envisioned as crossing the isthmus.

Question: Which two bodies of water border the isthmus?
Andaman Sea and to the east by the Gulf of Thailand