Is it legal to use DIAS on PSA KS47?
Does anyone tried to run full-auto before?
I'm planning to use 75rds drum for ultimate drum dump and save the wear & tear on my registered Polytech Spiker at the same time.
Any thoughts?

I don't see why not.  It's an AR lower with a different magwell.  I know guys have run the MGI that uses different magwell in 7.62AK and that Michaels Machines makes or used to make an AR lower setup for AK mags and a DIAS.  Have you shot a full auto 7.62X39?  I have shot a PWS upper that took AR pattern 7.62X39 mags and did not enjoy it.  I also shot one mag out of a real AK full auto and was not a fan.

I have shot a few full auto AK's over the years and they are not fun to shoot in my opinion.

Yeah, I thought it shouldn't be a issue since the internal is pretty much identical.

I think AK47 round in AR15 type rifle seems to produce more recoil and movement.
I love shooting my registered full-auto AK47... yes, they're rough and no way close to M16 refinement but that's the one reason I like it... rough
Pretty much I want something different with my DIAS...

Yea, I just bought a CMMG MKG .45 ACP "Pistol" to run with mine once it clears.  Not sure if you are interested in a pistol caliber but in semi auto it is very nice to shoot.  It's softer than a standard blowback but will run much longer than the DI .45's out there.  A buddy has an integral 9mm blowback AR and my CMMG .45 is noticeably softer recoil.  I took it to my dealers shop and tried dropping my RDIAS in and the hump is going to need about 1/16th off of it to fit with a needle file and will then drop in perfect.

MAC did a review of it on his channel with a fostech binary trigger and suppressor.  If that is any indication how fun it will be with the DIAS it will very fun.  .45 can be loaded inexpensive also if you are into reloading.  I am like you I think wanting to get the most out of my RDIAS with various hosts.