I am frequently contacted by people interested in doing fieldwork in Cambodia. For reasons I detail here, this is often difficult. However, there are several schools running fieldwork projects this summer in other parts of Southeast Asia. These are a good introduction to the archaeology of the region.
Ifugao Archaeological Project in the Philippines (Application Deadline: March 16th)
Summer archaeological Field School at Promtin Tai, Thailand (Application Deadline: February 15th).
Summer archaeological Field School in Krabi, Thailand (Application Deadline: February 15th)
AIA fieldwork scholarships (Application Deadline: March 1st)