Hi Molly, We flew with them in April and it was 25kg then.
If you check under "services" on the KTHY website and hover over "luggage" it does still say 25kg hold luggage.
I found them quick to respond when I emailed them - maybe try that if you want to be sure. My e-ticket actually stated 25kg and 5kg hand luggage.
Nice flight by the way - free drink and lunch included.