US$240,000 to retire in Asia

I've been trying to calculate how much money I'd need to retire in Asia. According to Retire Cheap Asia, you can live a frugal life in Asia with US$500 per month. A comfortable life would require US$1000 per month.

Now let us assume that you can get 5 per cent return on an investment. This means that you will need US$240,000 invested to give you $1,000 per month in passive income.

About half of this money should be invested in investments that provide stable passive income, as you will need this to give you the base $500 per month necessary for a frugal lifestyle. The rest can be invested in shares to protect against inflation.