The Kingdom of Funan was recorded by the Chinese as well, but of course their quite clear accounts of the place were ignored and/or denigrated, possibly because they are pre-muzzie. The excavations at Angkor Borai have shown, conclusively, that an artificial and quite navigable canal had existed (and in some places still does), and the strata at the former site of the city reach back at least as far as the 1st c BC. Lots of evidence of seagoing trade. Not much on the web search about Angkor Borai, that I saw. Thanks Red Badger!
Cattigara is thought to be the Roman name for the major port of the Magnus Sinus - the Ptolemic name for the Gulf of Thailand. The Roman Cattigara was Funan era Óc Eo (o'keo / glass canal), which is modern day Thoại Sơn District in Vietnam. There is a man made canal running from Angkor Borei south to Óc Eo that is believed to date from the Funan era.