Download distro key:

 wget http://ftp.th.pld-linux.org/dists/th/PLD-3.0-Th-GPG-key.asc

Verify it's validity

Import key to rpm:

 sudo rpm --import PLD-3.0-Th-GPG-key.asc

Checking installed keys:

rpm -qa gpg-pub*
gpg-pubkey-e64e7bf7-47b35206.(none)

Checkign details of given key:

rpm -qi  gpg-pubkey-e64e7bf7-47b35206

or

rpm -q gpg-pubkey --qf '%{name}-%{version}-%{release} --> %{summary}\n'

Import key to gpg keyring:

gpg --import PLD-3.0-Th-GPG-key.asc
gpg: key E4F1BC2D: public key "DSApub (PLD Linux Distribution 3.0 (Th)) <th-admin@pld-linux.org>" imported
gpg: key EAE6F8B8: public key "RSApub (PLD Linux Distribution 3.0 (Th)) <th-admin@pld-linux.org>" imported
gpg: Total number processed: 2
gpg:               imported: 2  (RSA: 1)

List installed gpg keys:

gpg --list-keys
/home/users/matkor/.gnupg/pubring.gpg
-------------------------------------
pub   1024D/E4F1BC2D 2008-02-13
uid                  DSApub (PLD Linux Distribution 3.0 (Th)) <th-admin@pld-linux.org>

pub   1024R/EAE6F8B8 2008-02-13
uid                  RSApub (PLD Linux Distribution 3.0 (Th)) <th-admin@pld-linux.org>

Verificaton details of given package (here we see missing key e4f1bc2d):

rpm -K ./0verkill-0.16-4.i686.rpm  -v
./0verkill-0.16-4.i686.rpm:
    Header V3 DSA signature: NOKEY, key ID e4f1bc2d
    Header SHA1 digest: OK (58b413f3e63ddad1503a43a64acd6187864fd33b)
    MD5 digest: OK (5f66e9757673f41e9d0ff3b28c521638)
    V3 DSA signature: NOKEY, key ID e4f1bc2d

Deleting multiple keys from rpm (specifies multiple packages error):

sudo rpm -e  --allmatches gpg-pubkey-e64e7bf7-47b35206