Mallakar Siamese da Vietnamese ya tsananta a cikin ƙarni na 17 da 18, wanda ya haifar da ƙaura daga kujerar mulki akai-akai yayin da ikon sarautar Khmer ya ragu zuwa yanayin vassal.Siam, wanda watakila an yi masa shari'a a matsayin abokin adawa da kutsawar Vietnam a karni na 18, ita kanta ta shiga cikin rikice-rikice da aka dade da Burma kuma a cikin 1767 babban birnin Siamese na Ayutthaya ya lalace gaba daya.Koyaya, Siam ya murmure kuma nan da nan ya sake tabbatar da ikonsa a kan Cambodia.An nada matashin sarki Khmer Ang Eng (1779-96) a matsayin sarki a Oudong yayin da Siam ya mamaye lardunan Battambang na Cambodia da Siem Reap.Sarakunan yankin sun zama ’yan boko a karkashin mulkin Siamese kai tsaye.^[72]Siam da Vietnam suna da halaye daban-daban game da dangantakarsu da Cambodia.Siamese sun yi tarayya da Khmer addini, tatsuniyoyi, adabi, da al'adu guda ɗaya, bayan sun ɗauki ayyukan addini da al'adu da yawa.^[73] Sarakunan Chakri na Thai sun bi tsarin Chakravatin na kyakkyawan shugaba na duniya, bisa ɗabi'a da kyautatawa suna mulkin dukan talakawansa.'Yan Vietnamese sun kafa wata manufa ta wayewa, yayin da suke kallon mutanen Khmer a matsayin marasa al'ada kuma suna ɗaukar ƙasar Khmer a matsayin halaltacciyar wurin mamaya daga Vietnam.^[74]Wani sabon gwagwarmaya tsakanin Siam da Vietnam don iko da Cambodia da mashigin Mekong a farkon karni na 19 ya haifar da mamayar Vietnam a kan wani sarkin Kambodiya.Ƙoƙarin tilasta wa 'yan Cambodia yin amfani da al'adun Vietnamese ya haifar da tawaye da yawa ga mulkin Vietnam.Mafi shahara ya faru daga 1840 zuwa 1841, yana yaduwa a yawancin ƙasar.Yankin Mekong Delta ya zama rikici na yanki tsakanin Cambodia da Vietnamese.A hankali Cambodia ta rasa iko da yankin Mekong Delta.