There is an extremely important text for the conflict in the 1830s between “Vietnam,” “Siam” and “Cambodia” that I have never seen an historian use before, and that is the The Strategy for Pacifying the Siamese Raiders and Thuận Bandits (Tiễu bình Tiêm khấu Thuận phỉ phương lược 勦平暹寇順匪方略).
This text contains very detailed information about the conflict between “Vietnam,” “Siam” and “Cambodia” in the early 1830s; much more detailed information than the Nguyễn Dynasty chronicles, The Veritable Records of Đại Nam (Đại Nam thực lục 大南寔錄), contains.
And from those details, one can gain very interesting insights into that conflict.