don't worry, the TM30 registration can be made personally on the Immigration on the next available working day after Immigration was closed. Take your wife with you, her Thai ID card, her blue housebook and your passport
if he followed your unsafe advice and Hua Hin would not accept the 800,000 THB that are in his Thai bank account since 20 years, because he cannot prove that the money - a long time ago! - came from abroad (which is the pre-requisite to be accepted for an application from a visa-exempt to an initial 90-days Non-O visa) he would be f....d. He would be forced to pay tea money. And he won't be very happy about your misleading advice.
like others said: The Immigraton officer at the border will sum up all touristic entries you did during the recent 365-days period. He can clearly see it on his computer. If the stays exceed a 180 days period in total, he is going to pull you aside. Your chances are higher if you have stayed abroad for a long spell between each entry, and if you didn't maximize every visa-exempt stay with an extension
However you can only get the "60-days family visit" extension, if your marriage is acknowledged and registered in Thailand. Because Immigration will want to see a freshly on the Amphur printed "Kor Ror 22" marriage registry as proof of a still existing marriage. If you marriage is only registered abroad, you first need to get it acknowledged inside Thailand
you most probably won't be able to do 6 consecutive months out of two visa-exempt entries and their 30 days extension. While it depends on the Immigration officer, it also depends on your stamp history of a recent 365-days period. If you did a touristic entry somewhere along that period, it will be counted against your plan
everything is correct, except the part that "before the visa expires". The 90-days Non-Imm-O Visa already expires and becomes used and invalid when you enter Thailand! What you meant is "before the 90-days stay permit expires"
Myself I would exactly do that, as long as there won't be any repucussions coming from Immigration, should they ask for your calendar year tax receipt when you apply for the next yearly extension. As far as I can see this won't happen, it has already been called off by many Immigration officials who have been interviewed on this matter. They don't want to do the job for the Thai Tax Department
you can google dual tax agreement and how it works . . . what I meant to say, John Stanners in the next comment put into more accurate words: "The tax you pay in the UK on the income you bring into Thailand can be claimed as a tax credit against Thai tax.". I changed my text accordingly