To disable password prompt create a password file and type the password.
This will be in plain text and does carry a security risk.
In the OpenVPN configuration file add the following line
askpass /etc/openvpn/password.txtto the end
#OpenVPN Server conf
tls-client
client
dev tun
proto udp
tun-mtu 1400
remote remote server ip
pkcs12 Asangapradeep.p12
cipher BF-CBC
verb 3
ns-cert-type server
askpass /etc/openvpn/password.txt
Set the password file location in the "secret file" attribute of OpenVPN applet.
OpenVPN applet will connect without a problem after this.