There are a lot of variables in that demographic you describe.
If you came to Thailand mid 40's, and say you left school at 15, that's 30 years of working, not 40 years of working.
Firstly, the type of occupation would matter greatly, which goes directly to the amount of salary earned. On this point, salaries were not very large back in those days, for all professions.
Then, there are possible losses along the way to consider. Eh: divorce, the GFC etc etc. All effect one's cash / asset portfolio. Divorce and loss of property and child support to pay being a common financial setback to many men in Australia.
There's also how many hours a week the person worked, and their tax rate, or if they were paid cash in hand, as well as the lifestyle they lived, and the investments they made.
Another thing to consider is, in general, humans are living longer. That 30 years of working now has to see you out for longer than in past generations.
The list goes on, but the above are some of the reasons people like yourself have returned back to Australia to do their 2 years to qualify for a pension.
It's not a bad deal. Work until mid 40's, move to a cheap country, get a pretty girl for cheap, don't work for the next 20 years, return home "cap in hand" for 2 years, get the pension, and then return back to the cheap country.
One may call it good financial planning, and a good work life balance. However, there are people who work from 15 to 65 in Australia, and will never qualify for a pension. I suspect they don't have kind words to say about the above people.