Thailand really needs the volunteers?

A quick search said all, in the ASEAN region, only Thailand , Loas, Cambodia and Vietnam  have volunteers coming in?

Why ? not other countries in ASEAN ?

http://www.thai-experience.org/

http://www.responsibletravel.com/TripSearch/Volunteer%20travel/ActivityCategory100011.htm?gclid=CJC067qzzY4CFSTjbgodlBo0Ag

http://www.volunteerabroad.com/Thailand.cfm

http://www.volunteer.org.nz/thailand/

http://www.openmindprojects.org/