As a general rule, income derived from an RP source is taxed in the RP. Income derived from a foreign source is not taxed in the RP but is probably taxed in the source country.
Things can be very different depending which other country is involved.
LOCK UP! so the countries have agreement against double taxation, so you don\'t risk to pay tax in both countries for SAME income.
I suppose tax for retirement pay normally are taxed in the countries who pay it.
The \"6 months rule\" is common to decide which country is counted as you are living there,
NOTE! It can be very interesting if
1. there are agreements against double taxation,
2. RP is counted as main country
3. AND the income is from working abroad a part of the year.
Then it seems no country want to tax that work income...

I know some use part of this to get REDUCED tax by working in Europe less than 6 months per year, and live in Thailand the rest of the year. Then they PAY income tax on that European income, BUT they pay the LOWER Thai income tax percent.