Students of Southeast Asian languagues will want to visit the The Southeast Asian Languages Library
at http://www.sealang.net/library. It is highly recommended as an excellent set of online dictionaries for mainland Southeast Asian languages. This website provides "bilingual and monolingual dictionaries, monolingual text corpora, aligned bitext corpora, and a variety of tools for manipulating, searching, and displaying complex scripts."
The site currently has resources for Thai, Burmese, Khmer, Lao, Shan, Karen, Mon, Vietnamese, Indonesian, Malay, Javanese, Balinese, Maranao and Maguinda-nao. Future plans include expansion in resources for the island Southeast Asian languages -Tagalog, Cebuano, Acehnese, Ilocano - and even more.