The issue is simple, if the loan goes bad and you want to recover your security... irrespective of the legalities the pressure on your wife to just let the money go will be massive compared to the pressure you are under now. security or not this is an unsecured loan and you have to ask yourself if you can afford and are willing to loose that money if it all goes tits up.
As for the course, i am under the impression that lawyers in commerical law at the top of their game and qualified in multiple legal systems are very sought after. but how useful it would be for this chap really does depend on just how clever he is and the usefulnenss of the anglo-thai combination. Due diligence rather than wishful thinking would be the orer of the day. has he approched potential employers to scope out their opinions? And in all seriousness would he be better off working for a firm for a few years and then going to the course, mba's straight of on university are not worth much.
my suggestion for what its worth
make an islamic style loan. wife buys the land and agrees a buy back price and a period of time for that buy back to be valid. deals with the ecurity issue as they lands in the wifes name until its paid back. but really its still going to be seen as family land and you will never be able to sell it.
a better option is to go back with the offer of free bed and board, which in reality will half the cost of the degree (assuming its the uk). and as a gift to cover the cost of the loan repayments during the course and for 1 year after he as finished or he gets a job... which ever comes first. They can then go and get a commercial loan against the the land.
from what I have seen Thai banks are very predatory and to be honest giving a 25% loan against land is something I would thought they would be very keen on even if they don't think the loan will be repaid.
This put yours better half to be offering to give the lad half of the costs, rest of the family to put up their half and take the risks of failure.