A karni na 14, daular Khmer ko Kambuja ta sha wahala mai tsawo, mai wahala, da ci gaba da raguwa.Masana tarihi sun ba da shawarar dalilai daban-daban don raguwa: juyin addini daga addinin Hindu na Vishnuite-Shivaite zuwa addinin Buddah na Theravada wanda ya shafi tsarin zamantakewa da siyasa, gwagwarmayar iko na cikin gida tsakanin sarakuna Khmer, tawaye na vassal, mamayewa na kasashen waje, annoba, da rushewar muhalli.Dangane da zamantakewa da addini, bangarori da dama sun taimaka wajen durkushewar Kambuja.Dangantaka tsakanin masu mulki da jiga-jigan su ba ta daidaita ba – a tsakanin sarakunan Kambuja 27, goma sha daya ba su da hakki na mulki, kuma an yi ta fama da tashin hankali.Kambuja ya fi mayar da hankali kan tattalin arzikinta na cikin gida kuma bai yi amfani da hanyar sadarwar kasuwancin teku ta duniya ba.Shigar da ra'ayoyin addinin Buddah kuma ya ci karo da da dagula tsarin jihar da aka gina a karkashin addinin Hindu.^[53]Masarautar Ayutthaya ta taso ne daga haɗin gwiwar jihohi uku na birni a kan ƙananan Chao Phraya Basin (Ayutthaya-Suphanburi-Lopburi).^[54] Daga karni na sha hudu zuwa gaba, Ayutthaya ya zama kishiyar Kambuja.^[55] Angkor ya yi wa Ayutthaya kawanya a shekara ta 1352, kuma bayan kama shi a shekara ta gaba, an maye gurbin sarkin Khmer da sarakunan Siamese.Sannan a shekara ta 1357, Sarkin Khmer Suryavamsa Rajadiraja ya sake karbar sarauta.^{[56 <]} > A cikin 1393, Sarkin Ayutthaya Ramesuan ya sake kewaye Angkor, ya kama shi a shekara mai zuwa.Dan Ramesuan ya mulki Kambuja na wani dan lokaci kafin a kashe shi.A ƙarshe, a cikin 1431, Sarkin Khmer Ponhea Yat ya watsar da Angkor a matsayin wanda ba zai iya karewa ba, kuma ya koma yankin Phnom Penh.^[57]Phnom Penh ya fara zama babban birnin Cambodia bayan Ponhea Yat, sarkin daular Khmer, ya mayar da babban birnin kasar daga Angkor Thom bayan da Siam ya kwace shi kuma ya lalata shi a shekarun baya.Phnom Penh ya kasance babban birnin sarauta na tsawon shekaru 73, daga 1432 zuwa 1505. A Phnom Penh, sarki ya ba da umarnin gina ƙasar don kare ta daga ambaliya, kuma a gina fadar.Don haka, ta sarrafa kasuwancin kogin Khmer, Siam na sama da masarautun Laotian tare da shiga, ta hanyar Mekong Delta, zuwa hanyoyin kasuwanci na kasa da kasa da suka hade gabar tekun kasar Sin, tekun Kudancin China, da Tekun Indiya.Ba kamar wadda ta gabace ta ba, wannan al'umma ta fi bude kofa ga waje kuma ta dogara ne kan kasuwanci a matsayin tushen arziki.Amincewa da cinikin teku tare dakasar Sin a lokacin daular Ming (1368-1644) ya ba da damammaki mai riba ga membobin jiga-jigan Cambodia waɗanda ke sarrafa ikon mallakar kasuwanci na sarauta.