Use the country name or you can search by the the names of peoples and languages, "Indonesian" for instance, or you can use "Indonesia" with the truncation symbol "Indonesia*" to find all instances of both "Indonesia" and "Indonesian." Try a keyword search first and look at the assigned Subject Headings to refine your search. Note that you can limit any search by date, document format, or language using the left-hand side-bar. This is a useful way to find Southeast Asian language materials.
General Note on Finding Historical Sources
History (can be divided by period), For primary sources, use Personal narratives, Sources
Try using the term Philippine Islands to find sources on the American period in the Philippines. Or Indochina for earlier works on Viet Nam Laos or Cambodia. Limit your search by date of publication.
Use Description and Travel as keywords to locate first-hand travel accounts. Limit by date. Limit to English for translations of foreign language accounts.
For memoirs and first-hand accounts, use Biography, Personal Memoirs, Personal Narratives