The Princess of Wales just posted a lengthy statement, in which she provides a pretty extensive health update after she announced she's battling cancer earlier this year. It's good news here ... as KM says she'll be in attendance for the Trooping of Colour parade Saturday.

Kate writes, "I am making good progress, but as anyone going through chemotherapy will know, there are good days and bad days. On those bad days you feel weak, tired and you have to give in to your body resting. But on the good days, when you feel stronger, you want to make the most of feeling well."

She continues ... "My treatment is ongoing and will be for a few more months. On the days I feel well enough, it is a joy to engage with school life, spend personal time on the things that give me energy and positivity, as well as starting to do a little work from home."

Finally, the Princess had this to say ... "I’m looking forward to attending The King’s Birthday Parade this weekend with my family and hope to join a few public engagements over the summer, but equally knowing I am not out of the woods yet."

She goes on to explain that she's learning to be patient with her ailment -- taking each day as it comes, and rolling with the punches. Kate ends by thanking everyone for the outpouring of love and support.

We broke the story ... Kate was expected to return to the public eye soon -- as we'd heard her cancer treatments were looking positive of late ... and that word of this would be coming down soon. Sure enough ... that happened, and now Brits can expect to see her in person.

It's a fantastic update -- and while it sounds like she has a long road ahead of her, this is certainly encouraging.