You didn't provide much info, but let's stay that PSI/Mandalay is on internal network 10.1.1.0 and PSI/Yangon is on internal network 10.1.2.0. If you configured a tunnel, then you should be able to verify that a tracert to the other site works. If it it does, then it obviously has to go through the tunnel because the Internet can't route those internal IP addresses. I presume that you already know that internal IP addresses at each site have to be different; otherwise it will never work.