TOP Postage and Phones . . . People like to stop at the post office often. Stamps with sticky stuff on the back are relatively new in SE Asia. In some places, you can only get stamps that you have to affix to your letters and post cards with glue from the glue pot. I suggest you bring a glue stick for this purpose.
Postage stamps make great souvenirs and gifts.
You can buy post cards from kids on the street everywhere. Phone calls can be made from your hotel, in some post offices, and in sidewalk phone stalls, but don t count on being able to use your calling card in many places. You may have to pay in cash to call home. Other than the obvious answer that it depends on where you are going, in general to get to locations in SE Asia, allow two days to get there and one day to get back. This is because you are going to cross the International Dateline, and you will lose a day going and gain a day coming back.