#!/bin/sh

PGPASS="passwod"

SQL="select col1 from hoge limit 1;"
PSQL="psql -h hostname -p 1234 -U admin -c '${SQL}' database"

COMMAND="export PGPASSWORD=${PGPASS}"
COMMAND="${COMMAND};${PSQL}"

result=`expect -c "
  spawn /usr/bin/ssh user@host -i /key.ppk "${COMMAND}"
  expect "Enter passphrase for key*"
  send "passwordn"
  interact;"`

echo ${result}

$ /bin/sh script.sh
spawn /usr/bin/ssh user@host -i /key.ppk [command]
Enter passphrase for key '/key.ppk':
[result]