There is now a Canadian Consular Office in Cambodia. If you need consular assistance you will need to contact the consular office. Note that the Canadian Embassy in Thailand is the Embassy to contact if the office does not have the level of consular assist you need. This can be when you require a new passport. The office in Cambodia will not be able to issue that.
Canadian Consular Office in Cambodia
The contact details for the office has been added below. The office is located in Phnom Penh if you need assistance. Should you lose your passport you should contact them for assistance with a travel document. The only office that can issue a new passport is the Canadian Embassy in Bangkok. Allow them to liase for you from Cambodia.
If you are getting married in Cambodia then you will need a letter of no impediment. This is to state that you are single. The office should be able to assist with this. You have to apply for the letter and then collect it when ready. This will need to be translated and certified. You can then use this in Cambodia to register your marriage in Cambodia as a Canadian.
Street Address: 27-29 Street 75, Sangkat Srah Chak, Khan Daun Penh, Phnom Penh, Cambodia
Telephone: +855 (0) 99 430 811
Email: PNPEN-Consular@international.gc.ca
You will note that there are other diplomatic missions in the region. These include the Canadian Embassy in Manila as well as the Canadian High Commision in Singapore as an example.