going by all the other types of visa financial proof requirements, the 500k has to be a physical cash amount in a recognised institution. Eg BOI wont accept crypto or share portfolios as proof of income, and unless pension/income documentation is certified by an embassy this is not allowed. (Most embassies will not certify now). Bank statements are the normal acceptable documents.
At CW they do require a new copy of your marriage certificate each year (not the pretty part) that you and your wife will have to get from the Amphur before applying for your extension.
by the law, yes for 3 months (as its in English), but in reality the police and dlt may give you a hard time if you dont have a supporting IDP from your home country. IDPs are a standard layout and are easy for non English authorities to understand, where as national licences are all different and not easy to interpret. Many police officers will insist you should have an IDP and that you are in the wrong, (but I have never seen any evidence of an official fine being issued for not having one and all other things are in order). However some insurance policies stipulate you must have a supporting IDP.
they dont want to exclude foreigners from the rule change, as there are many who try and avoid due tax in the same manner. Thailand has never been a tax haven, just lax.
The UK is pretty tight at taxing money, with a lot always being at source, so the recent changes shouldn't impact you that much apart from extra paperwork if you have already paid more tax in UK than you calculate you would owe on the money you brought in. And the proposed changes to looking at global income may actually benefit us, as it becomes easier to opt of some source based taxation in the UK and pay in Thailand at a reduced rate.
Via the airport, its not the number of entries that are a concern. They are concerned at the number of days previously spent in Thailand. You will have 120 on exemption/extension stamps, which in all probability will give rise to a warning to you that its the last time and to get a proper visa.
yes, its not those working abroad, but rather those that were investing abroad, leaving their earnings until a new financial year, and then transfering it into Thailand as excluded from tax income, many if not most not paying tax in the investment country as they weren't tax residents.