The thread type on that filter and most every other connection on the Yong Heng is M10x1mm.
You definitely need those white seals, but I think the problem you're running into is that your current seals have deformed enough to where they won't fit back in, or they might still fit but are too deformed to create a seal. M10 threaded connections require a seal to seal (if that makes sense). You can either use those white seals, or sometimes a dowdy seal is also used. In a pinch, you can gob on on Teflon tape and it might seal for a little bit, but it's definitely not the correct way to do it because M10 seals on the face and not the threads, like NPT. The white M10 seal goes inside the M10 female thread, then you screw in the M10 male fitting to crush the white seal and create an airtight seal. Note that it's possible to tighten the assembly too much, and you'll end up crushing the white seal to a point where the inner hole will collapse and prevent air from passing. It's one of those things where you want it tight enough, but not too tight.
I've converted most of my fitting on my Yong Heng and filtration setup over to 1/8 NPT. It's not cheap or all that practical to be honest, but I just hate dealing with M10 fittings partly for quality, and partly for availability because all that stuff has to come via slowboat from China. I just checked my parts bin and I have some extra white M10 seals. You can buy them off AliExpress or eBay, but if you only need a few like 2-3, I can try to put some in a regular envelope and hopefully the post office doesn't fuss about the envelope being too thick. Just let me know and I'm happy to send them out.
