If you get married in Cambodia then you will need to apply for a UK Spouse visa for your Cambodian wife. She will however require a TB test in order to obtain the and you can find the requirements for the TB test in Cambodia listed below. Note that the British Embassy in Cambodia will give you a list of requirements to obtain the visa and this is part of the process.
TB Test in Cambodia
Phnom Penh – International Organisation For Migration (IOM)
No. 281, Norodom Bld
Tai Ming building
Fax: 023 216 423
Note that only tests from this clinic will be accepted. You will need to contact them for an appointment and also note that 75 US dollars must be paid on the day of the chest X-ray examination at the clinic.