I haven't got anyone in trouble and he's an adult. Its not my opinion but Martin's. This type of Non O (retirement) has been going on for 13 years that I know of.
yes go for the 60-day VISA EXEMPT entry. Yes need exit from Thailand in 60 days. Possibly the airline may deny boarding as your return is 90-days with the airline you need to show a ticket out on day 60. Simply google onward travel and purchase on there. Its not expensive.
If you look well dressed are polite them immi won't usually ask.