Post-Angkor Khmer kingdom centered on the Mekong-river capital of Longvek, which prospered as a hub of Portuguese, Spanish, Malay, Chinese, and Japanese trade after the Khmer court relocated south from Angkor; ended by Siamese (Ayutthaya) conquest.
Sacked by an Ayutthaya (Siamese) invasion in 1594 CE during the Siamese–Cambodian War (1591-1594); King Satha II fled and the Longvek-centered kingdom collapsed, opening a fractured period of Siamese and Vietnamese intervention in Cambodian succession.
Verified fallback (same title/author already cited on the existing modern 'cambodia' canonical record): Chandler's standard scholarly history covers the post-Angkor Longvek period as a distinct chapter. No dedicated English-language Longvek-only monograph found on Open Library.