check the prices of UK universities for international students compared to locals and you will realize any dual pricing in Thailand is chump change. then check any high school textbook (or Google) for an explanation of why dual pricing ("price discrimination") is generally fairer and more efficient overall than a fixed single price.
many Thais study in the West paying tens of thousands of dollars more per year than local students. a few dollars extra for a hotel isn't such a big deal.
for private companies (in a well-functioning free market where consumers aren't being forced to purchase anything) - tiered pricing (or price discrimination) is superior to universal pricing - it allows more people overall to gain utility from the product/service as the equilibrium price for the groups with lower average spending power is lower than it would be if everyone paid the same price, and nobody pays more than they're happy to pay because it's a free market - (every high school economics textbook explains this well)
in most high-income countries, some private businesses charge more to working-age adults than to kids, students and the elderly, etc (because on average they can afford to pay more), and in most low-income countries, some private businesses charge more to foreign tourists (because on average they can afford to pay more)
Robert King you shouldn't believe everything you read in the Daily Mail - most UK universities charge international students tens of thousands of pounds more per year, for example
Do a bachelors degree and you will get a student visa for the duration - several Thai universities offer international programs taught completely in English - check out Chulalongkorn, Mahidol, Thammasat, ABAC, and Bangkok Uni.
I think you may be misunderstanding what FX rates are. The strength of the world economy overall is irrelevant. What matters is the RELATIVE strength (or weakness) of each of the national economies underlying those currencies.
I think you might need to re-read a few pages from your high school economics textbook. The USD has strengthened against the THB, EUR, and GBP, despite inflation (which is higher in the US than in Thailand, the Eurozone, and the UK), not because of it, and FX rates are determined by the relative strength of national economies, not the global economy (currency pairs aren't equities).
If you have some valuable skills / experience, you could set yourself up as a freelancer / consultant without investing much but you'll need another source of regular income (or some serious savings) while you build the business up to support your family. Getting a visa and work permit will also be a challenge and/or expense.
even pre-pandemic, hostels were over supplied in Bangkok, mostly because the barriers to entry are non-existent, so you will always be in a race to the bottom on price - very difficult to make decent profit unless it has +100 beds or you have mutiple properties in the same area (to achieve economies of scale) and/or you have a big pool that hipster-backpackers will pay a premium for.
however, some people do make good money by selling hostels (i.e. rent a townhouse, fill it with bunk beds, get it listed on the booking sites, and then sell it to a tourist/FOTB expat as a "hostel") so if you have good sales skills, can get the place for free, and can negotiate a rent holiday with the landlord for 6-12 months until tourists come back in any serious numbers, that might work.