Depends on time of year. A return flight in late December, originating in Bangkok is about 66% of thr price of a December flight originating in london. I assume because late December Bangkok London flights will be near empty, but London Bangkok flights very full.
Creates the same Permanent establishment doubt as LTR. The doubt is whether Thailand thinks your employer is creating taxable revenue in Thailand. They would then need to prove they are not by furnishing accounts. If not providing accounts, they risk a 5% fine on overall turnover.
My wife isn't. This thread is about the DTV and visas issued for entry ino Thailand, not about your own opinions about immigration into New Zealand. About 180,000 people immigrate into NZ each year. Of those, according to the government there, 14,000 are not meant to be there, from multiple years, chiefly visa overstayers. According to Immigration NZ, the largest group of illegal immigrants are from Tonga, followed by Samoa. Then China and India. I don't doubt there are Thais illegally staying in NZ (there was a hyped report of 100 fruit pickers being picked up, with papers from AEC Thai Development), just as there are Kiwis living illegally in Thailand (eg these losers:
/no-rights-kiwi-held-in-thai-detention-centre-says-illegal-travel-not-worth-it.html, https://www.nzherald.co.nz/nz/kiwi-who-overstayed-his-visa-by-2173-days-arrested-in-pattaya-facing-deportation-from-thailand/HUABCON37ZEVHOWZFUZHLUTFN4/). Curiously, in raids, Indians and Chinese are disproportionally picked up, not Tongans and Samoans, suggesting a racial element to law enforcement, not a surprise given the history of ANZ post-WW2. Indeed, this assertion is backed up by NZ Immigration Officers target "slow moving targets" and are discriminatory. New Zealanders have plenty of history illegally immigrating into other countries.
The intent of proof of funds is to demonstrate you are able to support yourself. Its a fairly common thing countries do; that visitors have the means to support themselves, to be able to return home etc.. If the 500,000 Baht/13,700 Euro is a gift then fine, but it seems a similar scam to those Agents who momentarily deposit money in an account so someone can meet the retiree requirement. Its corrupt. The DTV provides for a sponsorship letter. This would be the correct way, rather than trying to pass off someone else's money as your own. Of course, what you are suggesting is that people are all fundementally dishonest, and that everyone will empty their account the very next day. And in the same way, bank account statements, and other documents, submitted to European and North American companies mean nothing at all, because the account could be emptied and closed the very next day. But in actuality, most people do not do this. Now, in general, a country's insistance that an alien has the means to support themselves while visiting, is a very good thing. Someone who apparently has nothing to their name, and has to borrow 13,000 Euros to fly half way around the world, that seems somewhat questionable, bordering on irresponsible. I assume they can't even afford expatriate health insurance to support their 5 year bumming around Thailand. Better for their friend to formally assume full legal responsibility for their friend's financial affairs. The knock back for others, trying to obey the rules, is that Thailand might tighten up (will tighten up). I see the Thai MP who is Chair of their Industry Panel has already been muttering about visas, after billboards have been spotted in and around Bangkok, in Chinese, promising Thai passports. Thais are rightfully suspicious of foreigners who seek to exploit grey areas in their visa legislation.
I assume you are not loaning the money, and expect it back, because otherwise you are both conspiring to commit immigration fraud. Probably not a good idea if you live in Thailand, to post this in a public group.
The US constantly reviews immigration practices. Just a day ago, Canada announced changes to cut work permits by 30% this year and 10% in successive years. A lot of the time immigration rules are driven by reciprocity, and the US drives a lot of this. But 2 out of 3 countries you named have political climates that are generally anti-immigration, and that's driving legislative changes. You are surely aware of the recent fallout of the French elections, plus upcoming US elections where it's looking increasingly likely the challenger will win the electoral college vote. All these things will drive churn in legislation that you claim has hardly changed.