So many collections of resources have been digitized (though there's way more that's yet to be made available that way). While some of these are behind paywalls in subscription databases, others are freely available online. Googling topics of interest, along with phrases like "primary sources," "digital collections," etc. may yield results. Also think about who might care about this topic? If it's related to a certain region, look for museums, libraries, and historical societies in that area, and then see if they have digital archives.
Note: most primary sources will be written in the language of the relevant location. So if you're studying Malaysian history, but don't read Malay, that's going to limit the options you have.
Below is a link to one big clearinghouse of Asian Studies primary sources, and two newspaper databases that DePauw subscribes to.