While it may not be enough for you....that's probably twice as much as the typical old codger here has saved up if the fact many use agents because they don't have 800k baht to deposit for extensions is an iny indicator. With pension(s) and portfolio generating dividends...more than enough unless you are spending more than 100K baht monthly.
That is about 400,000 US dollars for reference. Invested conservatively in a portfolio generating 3 % per annum:
$12,000 US annually or $1000 per month
After estimated 28% tax rate, that's $720 net per month or 23,000 baht monthly.
Supplementing that with pension and one couold conceivably live comfortably.
How much pension is the question he needs to answer....apologies if stated already but did not go back and read every post.