Reason to return seems to be the big one. People talk about back to her high-earning job. I would say that it is important to also talk about caring responsbilities she has to come back to and can only be away from for a few weeks. Caring for her dear old Dad who has all manner of health problems. Cousins can only step in for her doing this work for a few weeks.
And since one of the best arguments that she will return home is that she is a carer here that caring role here would limit her ability to be away from Thailand to a short time.
A ridiculous question. We all have different levels of risk tolerance. That is the question for you not where shall I put it.? That said if it really is only a couple of K USD does it need fine-tuned calculation? Would it really matter if you lost the lot? Answer that question. Then do a bit of Googling around volatility and markets. High volatility = High returns. But High volatility = High risk. It's that simple for you to locate the choices you should make, now and in the future. Not ask Facebook.
Note all my comments about lack of free NHS service in all but very few cases where the patient has worked overseas for a British connected business. Otherwise free NHS goes after 2 years. It is resdience not nationality, passport of National Insurance contribution-based. It isn't good advice to go to a country wheer private costs are not at US or Japanese levels, but nonetheless are very high. The same is true for legal fees - wildly high.
Note my point about no free NHS access if out of UK for 2years or more. Entitlement is based on residencce, not nationality, passport of National Insurance contributions. The one exception is if you have been overseas working for a firm with a British Connection. Why do Brits keep continuing a belief in a fantasy rather than checking reality in healthcare before leaving the country? Residence is now the be all to end all and not just in health care, but, as an example accessing public housing.
and others If any good comes out of this let it be Brits understanding that if out of UK for 2+ years they have lost free access to NHS. You pay as a foreigner and sometimes NHS is more expensive than private, if probably mostly not. Entitlement is through residence not nationality, passport or having paid National Insurance. The one exception to the two year rule is if while overseas you have been working for a British firm.
Carry-in is the only assured way with Thailand. Books are supposedly OK to send duty free but I Am not sure on VAT. But western businesses often send as printed matte and you pay anyway. It has to be books. Personally though I will only carry-in.