2k pounds is not too bad. Remember, the person has to eat and stay somewhere as well and prepare themselves to leave. I don't know other parts of the circumstances, such as if there are unpaid medical bills or a dependent involved. What will he do once he is back in his home country? Needs some cash for that also. Of course today 2k pounds is worth about 20-30% less than it was 2 years ago thanks to Brexit.
Indeed you can handle an overstay yourself. Never go to a land border. Go to an international airport with a ticket in hand and arrive about 3-4 hours prior to departure. You do need the 500 THB/day (20,000 THB maximum) cash in hand when you go through departure immigration. The immigration officer will steer you to the overstay room where you pay a fine, get a stamp, and be on your way to the terminal to await your flight. But with the new Good Guys In, Bad Guys Out program....casual overstaying >90 days is now subject to blacklisting.
In the past, you could overstay for years [sic] and just show up at airport with 20k baht and be on your way. You could literally come back into Thailand the same or next day. But now if you turn yourself in at an airport 'border' you get blacklisted for:
>90 days overstay = 1 year blacklist
>1 year overstay = 3 years blacklist
>3 years overstay = 5 years blacklist
>5 years overstay = 10 years blacklist
If you get caught out casually and they find out you are on overstay, it is more severe:
\<1 year overstay = 5 years blacklist
>1 year overstay = 10 years blacklist
A lawyer can help, but really it would only be necessary if you wish to avoid the blacklisting. A Thai judge can actually reduce the overstay fine and remove some or all of the blacklisting time that you have accumulated. But it is not guaranteed...you are rolling the dice. It would probably be better to leave first, then retain a legit thai lawyer once abroad that will then work to reduce your 'blacklist' sentence.
This was all writing on the wall anyway. Did visitors really think that a country trying to develop itself and trade with other developed countries could just openly allow unlimited overstay without any serious penalty? And even those who were barely legal with unlimited Visa Exempt stamps....it was good while it lasted. But that loophole has tightened as well over the last 3 years or so. You can still come to thailand easily on a Visa Exempt or Tourist Visa. But to stay long term, you have to think long term (visiting family, retirement, business, certain educational goals, or save up for the Elite Visa).