The post office is located on the river road. You can buy stamps there and the service is reliable. They also have Express Mail Service (EMS) for your convenience.
There are several internet places around town, including a couple of shops on the old bridge road near the traffic circle. There is also internet at some of the guesthouses around town and at least one is set up for WiFi.
There are a couple of phone shops on Rte #3 near the market. The Internet shops also offer international phone/fax, sometimes inexpensive internet phone.